7 Forces in Fluids Compression guide: Chapter Planning Guide · 7 Forces in Fluids Chapter Planning...

Compression guide:To shorten instructionbecause of time limitations,omit Section 3.

OBJECTIVES LABS, DEMONSTRATIONS, AND ACTIVITIES TECHNOLOGY RESOURCES

7 Forces in FluidsChapter Planning Guide

Chapter Opener

177A Chapter 7 • Forces in Fluids

OSP Lesson Plans (also in print) TR Bellringer Transparency* TR LINK TOLINK TO LIFE SCIENCELIFE SCIENCE L6 Math Focus:

Surface Area-to-Volume Ratio* TR P24 Exhaling, Pressure, and

Fluid Flow*CD Science Tutor

TE Demonstration Building Pressure, p. 181g TE Connection Activity Language Arts, p. 181g TE Connection Activity Earth Science, p. 182g SE Quick Lab Blown Away, p. 184g

CRF Datasheet for Quick Lab* LB Whiz-Bang Demonstrations The Rise and Fall of

Raisins,* Going Against the Flow*g

Section 1 Fluids and Pressure• Describe how fluids exert pressure.• Analyze how atmospheric pressure varies with depth.• Explain how depth and density affect water pressure.• Give examples of fluids flowing from high to low

pressure.

OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P25 Shape and Overall Density* TR P26 Controlling Density Using

Ballast Tanks* SE Internet Activity, p. 189g

CRF SciLinks Activity*gVID Lab Videos for Physical Science CD Interactive Explorations CD-ROM

Sea the LightgCD Science Tutor

TE Demonstration Density Layers, p. 186g SE School-to-Home Activity Floating Fun, p. 187g TE Connection Activity Math, p. 187a TE Activity Making Models, p. 188g TE Connection Activity Math, p. 188a SE Connection to Geology Floating Rocks, p. 189g TE Group Activity Buoyancy and Scuba Diving, p. 189g SE Quick Lab Ship Shape, p. 190g

CRF Datasheet for Quick Lab* SE Skills Practice Lab Fluids, Force, and Floating, p. 198g

CRF Datasheet for Chapter Lab* SE Skills Practice Lab Density Diver, p. 718g

CRF Datasheet for LabBook*

PACING • 90 min pp. 186–191Section 2 Buoyant Force• Explain the relationship between fluid pressure and

buoyant force.• Predict whether an object will float or sink in a fluid.• Analyze the role of density in an object’s ability to

float.• Explain how the overall density of an object can be

changed.

OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P27 Wing Design and Lift* TR P28 Bernoulli’s Principle and the

Screwball*CD Science Tutor

TE Demonstration Magic Water, p. 192g TE Activity Pressure Analogy, p. 193b TE Activity Wing Shape, p. 193a TE Demonstration Flying Ball, p. 193g SE Connection to Social Studies The First Flight, p. 194g TE Activity Wind Tunnels, p. 194a TE Connection Activity Language Arts, p. 195g TE Group Activity Floating Bubbles, p. 195 ◆g

SE Science in Action Math, Social Studies, and LanguageArts Activities, pp. 204–205g

LB EcoLabs & Field Activities What’s the Flap AllAbout?*b

LB Long-Term Projects & Research Ideas Scuba Dive*a

PACING • 45 min pp. 192–197Section 3 Fluids and Motion• Describe the relationship between pressure and fluid

speed.• Analyze the roles of lift, thrust, and wing size in flight.• Describe drag, and explain how it affects lift.• Explain Pascal’s principle.

OSP Parent Letter ■

CD Student Edition on CD-ROM CD Guided Reading Audio CD ■

TR Chapter Starter Transparency*VID Brain Food Video Quiz

SE Start-up Activity, p. 179gpp. 178–185PACING • 90 min

CRF Vocabulary Activity*g SE Chapter Review, pp. 200–201g

CRF Chapter Review* ■g

CRF Chapter Tests A* ■g, B*a, C*s SE Standardized Test Preparation, pp. 202–203g

CRF Standardized Test Preparation*gCRF Performance-Based Assessment*gOSP Test Generator, Test Item Listing

CHAPTER REVIEW, ASSESSMENT, ANDSTANDARDIZED TEST PREPARATION

PACING • 90 min

Online and Technology Resources

Visit go.hrw.com foraccess to Holt OnlineLearning, or enter thekeyword HP7 Homefor a variety of freeonline resources.

This CD-ROM package includes:• Lab Materials QuickList Software• Holt Calendar Planner• Customizable Lesson Plans• Printable Worksheets

• ExamView® Test Generator• Interactive Teacher’s Edition• Holt PuzzlePro®

• Holt PowerPoint® Resources

STANDARDS CORRELATION SKILLS DEVELOPMENT RESOURCES SECTION REVIEW AND ASSESSMENT CORRELATIONS

Chapter 7 • Chapter Planning Guide 177B

CRF Directed Reading A* ■b, B*s IT Interactive Textbook* Struggling ReadersStruggling Readers

CRF Vocabulary and Section Summary* ■g

SE Reading Strategy Brainstorming, p. 180g SE Math Focus Pressure, Force, and Area, p. 181g TE Inclusion Strategies, p. 183 TE Support for English Language Learners, p. 183 MS Math Skills for Science The Pressure Is On!*g MS Math Skills for Science Density*g

SE Reading Checks, pp. 181, 182, 184g TE Homework, p. 181a TE Homework, p. 182g TE Reteaching, p. 184b TE Quiz, p. 184g TE Alternative Assessment, p. 184a SE Section Review,* p. 185 ■g

CRF Section Quiz* ■g

SAI 1; ST 2; PS 1a



SE Reading Strategy Discussion, p. 186g TE Reading Strategy Prediction Guide, p. 187g SE Math Focus Finding Density, p. 188g TE Support for English Language Learners, p. 189

SE Reading Checks, pp. 187, 188, 190g TE Homework, p. 187g TE Reteaching, p. 190b TE Quiz, p. 190g TE Alternative Assessment, p. 191g SE Section Review,* p. 191 ■g


SAI 1; ST 2; HNS 3; PS 1a, 2c;Chapter Lab: SAI 1; LabBook:SAI 1



SE Reading Strategy Reading Organizer, p. 192g TE Inclusion Strategies, p. 194 TE Support for English Language Learners, p. 195

CRF Reinforcement Worksheet Building Up Pressure*bCRF Critical Thinking Build a Better Submarine*a

SE Reading Checks, pp. 193, 195, 196g TE Homework, p. 195g TE Reteaching, p. 196b TE Quiz, p. 196g TE Alternative Assessment, p. 196g SE Section Review,* p. 197 ■g


UCP 5; SAI 1; ST 2; SPSP 5;HNS 3

SE Pre-Reading Activity, p. 178gOSP Science Puzzlers, Twisters & Teasersg

National ScienceEducation Standards

SAI 1, 2; ST 2

CRF Chapter Resource File SS Science Skills Worksheets IT Interactive TextbookOSP One-Stop Planner MS Math Skills for Science Worksheets * Also on One-Stop Planner

SE Student Edition LB Lab Bank CD CD or CD-ROM ◆ Requires advance prepTE Teacher Edition TR Transparencies VID Classroom Video/DVD ■ Also available in Spanish

KEY

Maintained by the NationalScience Teachers Association.See Chapter Enrichment pagesthat follow for a complete listof topics.

www.scilinks.orgCheck out Current Sciencearticles and activities byvisiting the HRW Web siteat go.hrw.com. Just typein the keyword HP5CS07T.

• Lab Videos demonstratethe chapter lab.

• Brain Food Video Quizzeshelp students review thechapter material.

ClassroomVideos

Holt Lab GeneratorCD-ROM

Search for any lab by topic, standard,difficulty level, or time. Edit any labto fit your needs, or create your ownlabs. Use the Lab Materials QuickListsoftware to customize your labmaterials list.

• Guided Reading Audio CD(Also in Spanish)

• Interactive Explorations• Virtual Investigations• Visual Concepts• Science Tutor

ClassroomCD-ROMs

Planning ResourcesTEST ITEM LISTINGPARENT LETTERLESSON PLANS

Visual ResourcesCHAPTER STARTER

TRANSPARENCYBELLRINGER

TRANSPARENCIES

CONCEPT MAPPINGTRANSPARENCYTEACHING TRANSPARENCIES

TEACHING TRANSPARENCIES

TEST ITEM LISTING

Copyright © by Holt Rinehart and Winston All rights reserved

The World of ScienceMULTIPLE CHOICE

1. A limitation of models is thata. they are large enough to see.b. they do not act exactly like the things that they model.c. they are smaller than the things that they model.d. they model unfamiliar things.Answer: B Difficulty: I Section: 3 Objective: 2

2. The length 10 m is equal toa. 100 cm. c. 10,000 mm.b. 1,000 cm. d. Both (b) and (c)Answer: B Difficulty: I Section: 3 Objective: 2

3. To be valid, a hypothesis must bea. testable. c. made into a law.b. supported by evidence. d. Both (a) and (b)Answer: B Difficulty: I Section: 3 Objective: 2 1

4. The statement "Sheila has a stain on her shirt" is an example of a(n)a. law. c. observation.b. hypothesis. d. prediction.Answer: B Difficulty: I Section: 3 Objective: 2

5. A hypothesis is often developed out ofa. observations. c. laws.b. experiments. d. Both (a) and (b)Answer: B Difficulty: I Section: 3 Objective: 2

6. How many milliliters are in 3.5 kL?a. 3,500 mL c. 3,500, 000 mLb. 0.0035 mL d. 35,000 mLAnswer: B Difficulty: I Section: 3 Objective: 2

7. A map of Seattle is an example of aa. law. c. model.b. theory. d. unit.Answer: B Difficulty: I Section: 3 Objective: 2

8. A lab has the safety icons shown below. These icons mean that you should weara. only safety goggles. c. safety goggles and a lab apron.b. only a lab apron. d. safety goggles, a lab apron, and gloves.Answer: B Difficulty: I Section: 3 Objective: 2

9. The law of conservation of mass says the tot al mass before a chemical change isa. more than the total mass after the change.b. less than the total mass after the change.c. the same as the total mass after the change.d. not the same as the total mass after the change.Answer: B Difficulty: I Section: 3 Objective: 2

10. In which of the following areas might you find a geochemist at work?a. studying the chemistry of rocks c. studying fishesb. studying forestry d. studying the atmosphereAnswer: B Difficulty: I Section: 3 Objective: 2

TEACHER RESOURCE PAGE

Lesson Plan

Section: Waves

PacingRegular Schedule: with lab(s):2 days without lab(s):2 days

Block Schedule: with lab(s): 1 1/2 days without lab(s): 1 day

Objectives1. Relate the seven properties of life to a living organism.

2. Describe seven themes that can help you to organize what you learn aboutbiology.

3. Identify the tiny structures that make up all living organisms.

4. Differentiate between reproduction and heredity and between metabolismand homeostasis.

National Science Education Standards CoveredLSInter6: Cells have particular structures that underlie their functions.

LSMat1: Most cell functions involve chemical reactions.

LSBeh1:Cells store and use information to guide their functions.

UCP1:Cell functions are regulated.

SI1: Cells can differentiate and form complete multicellular organisms.

PS1: Species evolve over time.

ESS1: The great diversity of organisms is the result of more than 3.5 billion yearsof evolution.

ESS2: Natural selection and its evolutionary consequences provide a scientificexplanation for the fossil record of ancient life forms as well as for the strikingmolecular similarities observed among the diverse species of living organisms.

ST1: The millions of different species of plants, animals, and microorganismsthat live on Earth today are related by descent from common ancestors.

ST2: The energy for life primarily comes from the sun.

SPSP1: The complexity and organization of organisms accommodates the needfor obtaining, transforming, transporting, releasing, and eliminating the matterand energy used to sustain the organism.

SPSP6: As matter and energy flows through different levels of organization ofliving systems—cells, organs, communities—and between living systems and thephysical environment, chemical elements are recombined in different ways.

HNS1: Organisms have behavioral responses to internal changes and to externalstimuli.

This CD-ROM includes all of theresources shown here and thefollowing time-saving tools:

• Lab Materials QuickListSoftware

• Customizable lesson plans

• Holt Calendar Planner

•The powerfulExamView® TestGenerator

Chapter Resources

Dear Parent,

Your son's or daughter's science class will soon begin exploring the chapter entitled “The

World of Physical Science.” In this chapter, students will learn about how the scientific

method applies to the world of physical science and the role of physical science in the

world. By the end of the chapter, students should demonstrate a clear understanding of the

chapter’s main ideas and be able to discuss the following topics:

1. physical science as the study of energy and matter (Section 1)

2. the role of physical science in the world around them (Section 1)

3. careers that rely on physical science (Section 1)

4. the steps used in the scientific method (Section 2)

5. examples of technology (Section 2)

6. how the scientific method is used to answer questions and solve problems (Section 2)

7. how our knowledge of science changes over time (Section 2)

8. how models represent real objects or systems (Section 3)

9. examples of different ways models are used in science (Section 3)

10. the importance of the International System of Units (Section 4)

11. the appropriate units to use for particular measurements (Section 4)

12. how area and density are derived quantities (Section 4)

Questions to Ask Along the Way

You can help your son or daughter learn about these topics by asking interesting questions

such as the following:

• What are some surprising careers that use physical science?

• What is a characteristic of a good hypothesis?

• When is it a good idea to use a model?

• Why do Americans measure things in terms of inches and yards instead of centimeters

and meters ?

Math Focus: Surface Area—to-Volum

e Ratio

Copyright © by Holt, Rinehart and Winston. All rights reserved.

TEACH

ING

TRA

NSPA

REN

CY

Surface A

rea–to-Volume

Ratio

Calcu

late th

esu

rface area–to-volum

e ratio of a cube w

hose

sides m

easure 2 cm

.

Step 1: Calcu

late the su

rface area.

surface area of cube � num

ber of sides �

area of side

surface area of cube�

6�

(2 cm�

2 cm)

surface area of cube�

24 cm2

Step 2: Calcu

late the volu

me.

volume of cube �

side � side �

side

volume of cube

� 2 cm

� 2 cm

� 2 cm

volume of cube �

8 cm3

Step 3: Calcu

late th

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ratio.

Now

It’s Your Turn1. C

alculate

the

surface

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be wh

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long.

2. Calcu

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ratio of a cube w

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TEACHING TRANSPARENCY

Wing Design and Lift

bAirplane wings are made sothat the air speed above thewing is greater than the airspeed below the wing.

According to Bernoulli’s principle,a difference in air speed means adifference in pressure. The resultis an upward force that contrib-utes to lift.

Another feature of wingdesign is that the shapeof the wing forces theair downward. So, the airpushes the wing upward.

a

c

P27

177C Chapter 7 • Forces in Fluids

7

Shape and Overall Density

TEACH

ING

TRA

NSPA

REN

CY

Copyright ©

by Holt, R

inehart and Winston. A

ll rights reserved.

A block of steelis m

ore densethan w

ater, so itsinks.

Shaping the steelinto a hollow

formincreases the volum

eoccupied by the sam

em

ass. The overalldensity of the ship isreduced. The ship isless dense than w

ater,so the ship floats.

P25

Chapter: Cells: The Basic Units of Life

Forces in Fluids CHAPTER STARTER

You’re the pilot of a revolutionary newundersea vessel, Deep Flight, and todayis the day of your first undersea voyage.Your destination: the Mariana Trench,which is the deepest spot in the ocean.The Mariana Trench is about 11 kmdeep—that’s deep enough toswallow Mount Everest, thetallest mountain in theworld. Fewer than a dozenundersea vessels have everventured this far down. Thereason? Water exertstremendous pressure at thisdepth. Luckily, Deep Flight’shull is made of an extremelystrong ceramic material that can with-stand the pressure.

What makes Deep Flight so revolu-tionary? Deep Flight actually “flies”through the water. In fact, Deep Flightlooks a lot like an airplane with stubbywings. Controls allow you to adjust thecurvature of the wings to move fasterthrough the water.

With its battery-powered motor and yourability to change the curvature of the wings,Deep Flight can reach speeds of up to25 km/h! By adjusting Deep Flight’s wingflaps and tail fins, you can do dives, spins,and turns. Ready to race a whale?

As futuristic as this story sounds, DeepFlight is a real undersea vessel that iscurrently being tested. Although DeepFlight has not yet made it to the bottomof the Mariana Trench, some scientistsbelieve this type of undersea vessel willone day be used routinely to explore theocean floor.

In this chapter you will explore flu-ids. You’ll learn how pressure is exertedby water and other fluids. You’ll also learnwhy some things sink and others float.Dive in!


Imagine . . .

Forces in Fluids BELLRINGER TRANSPARENCY


Section: Fluids and PressureImagine the following situation:

One afternoon, you go outside to find youryounger sister standing by her bike with a nail inher hand. The bike has a flat tire. She wants toknow why the air came out of the tire when shepulled the nail out.

Write a few sentences in your science journal toexplain why air rushes out of a hole in a tire.

Section: Buoyant ForceIdentify which of the following objects will float inwater: a rock, an orange, a screw, a quarter, a candle,a plastic-foam “peanut,” and a chalkboard eraser.

Write a hypothesis in your science journal aboutwhy an aircraft carrier, which weighs thousands oftons, does not sink.


TEACH

ING

TRA

NSPA

REN

CY

Exhaling, Pressure, and Fluid Flow

When you exhale,

a muscle in your

chest moves up-

ward and decreases

the space in yourchest.

a

The decrease in spacecauses the pressure inyour lungs to increase.The air in your lungsflow

s from a region

of high pressure (yourchest) to a region oflow

pressure (outsideof your body).

b

Exhaled air carriescarbon dioxide outof the lungs.

c

P24


TEACH

ING

TRA

NSPA

REN

CY

Controlling Density Using Ballast Tanks

When a subm

arine is floatingon the ocean’s surface, itsballast tanks are filled m

ostlyw

ith air.

Vent holes on the ballast tanksare opened to allow

the subma-

rine to dive. Air escapes as the

tanks fill with w

ater.

Vent holes are closed, and com-

pressed air is pumped into the

ballast tanks to force the water

out, so the submarine rises.

Air

Ballast tan

ks

P26


TEACH

ING

TRA

NSPA

REN

CY

Bernoulli’s Principle and the ScrewballD

irectionof airflow

Direction

of spin

Because air pressure on the

left side is greater than airpressure on the right side, theball is pushed tow

ard the rightin a curved path.

c

aAir speed on the left side of the ball is decreasedbecause air around the ball m

oves in the oppositedirection of the airflow

. So, there is a region ofincreased pressure on the left side of the ball.

Air speed on the right side of the ball is increasedbecause air around the ball m

oves in the same

direction as the airflow. So, there is a region of

decreased pressure on the right side of the ball.

b

P28

whichincreases

with

which differdue to the fluids’

oxygen

such asexert

such as

Forces in Fluids CONCEPT MAPPING TRANSPARENCY


Use the following terms to complete the concept map below:depth, density, water pressure, pressure, atmospheric pressure,fluids, water

SAMPLE SAMPLE SAMPLE

Meeting Individual Needs

Review and Assessments

Labs and Activities

DIRECTED READING A VOCABULARY ACTIVITY REINFORCEMENT

ECOLABS & FIELD ACTIVITIES

DATASHEETS FOR QUICKLABS

DATASHEETS FOR QUICK LABS

STANDARDIZED TEST PREPARATIONCHAPTER TEST BCHAPTER REVIEWSECTION QUIZ

SCILINKS ACTIVITY

MARINE ECOSYSTEMS

Go to www.scilinks.com. To find links relatedto marine ecosystems, type in the keywordHL5490. Then, use the links to answer thefollowing questions about marine ecosys-tems.

1. What percentage of the Earth’s surface iscovered by water?

2. What percentage of the Earth’s water is found in the oceans?

3. What is the largest animal on Earth?

4. Describe an ocean animal.

Name Class Date

SciLinks ActivityActivity

Developed and maintained by theNational Science Teachers Association

Topic: Reproductive SystemIrregularitiesSciLinks code: HL5490


Name Class Date

Vocabulary ActivityActivity

Getting the Dirt on the SoilAfter you finish reading Chapter: [Unique Title], try this puzzle! Use the clues belowto unscramble the vocabulary words. Write your answer in the space provided.

1. the breakdown of rock intosmaller and smaller pieces:AWERIGNETH

2. layer of rock lying beneath soil:CROKDEB

3. type of crop that is plantedbetween harvests to reduce soilerosion: CROVE

4. action of rocks and sedimentscraping against each other andwearing away exposed surfaces:SABRONIA

5. a mixture of small mineral frag-ments and organic matter: LISO

6. rock that is a source of soil:PRATEN CORK

7. type of reaction that occurs whenoxygen combines with iron toform rust: oxidation

8. type of weathering caused byphysical means: CLEMANIACH

9. the chemical breakdown of rocksand minerals into new substances: CAMILCHETHEARIGWEN

10. layers of soil, to a geologist:SNORHIZO

11. the uppermost layer of soil:SPOTOIL

12. process in which rainwater car-ries dissolved substances fromthe uppermost layers of soil to thebottom layers: HELANCIG

13. small particles of decayed plantand animal material in soil:MUUSH

14. the process in which wind, water,or ice moves soil from one location to another: ROOSINE

15. the methods humans use to takecare of soil:OSIL VASETONRICON

LONG-TERM PROJECTS & RESEARCH IDEAS

WHIZ-BANGDEMONSTRATIONS

VOCABULARY AND SECTION SUMMARY


Section: EnergIn the space provided, write the letter of the description that best matches theterm or phrase.

______ 1. building molecules that can be used asan energy source. or breaking down moleculesin which energy is stored

______ 2. the process by which light energy is convertedto chemical energy

______ 3. an organism that uses sunlight or inorganicsubstances to make organic compounds

______ 4. an organism that uses sunlight or inorganicsubstances to make organic compounds

______ 5. an organism that consumes food to get energy

______ 6. the process of getting energy from food

In the space provided, write the letter of the term or phrase that best completeseach statement or best answers each question.

Name Class Date

Section QuizAssessment

a. photosynthesis

b. autotroph

c. heterotroph

d. cellular respiration

e. metabolism

f. cellular respiration

______ 7. Which of the following mostclosely resembles cellularrespiration?a. warm water moving

through copper pipesb. people movimg alomg a

escalatorc. mixing different foods in

a blenderd. logs burning in a fire

______ 8. An organism’s reproductivecells, such as sperm or eggcells, are called?a. genesb. chromosomesc. gamates.d. zygotes.

______ 9. An organism’s reproductivecells, such as sperm or eggcells, are called?a. genesb. chromosomesc. gamates.d. zygotes.

______10. Which of the following mostclosely resembles cellularrespiration?a. warm water moving

through copper pipesb. people movimg alomg a

escalatorc. mixing different foods in

a blenderd.

logs burning in a fire


Section: ExploringTHAT’S SCIENCE!

1. How did James Czarnowski get his idea for the penguin boat, Proteus?Explain.

2. What is unusual about the way that Proteus moves through the water?

MATTER + AIR ➔ PHYSICAL SCIENCE

3. What do air, a ball, and a cheetah have in common?

4. What is one question you will answer as you explore physical science?

5. Chemistry and physics are both fields of . Chemists

study the different forms of and how they interact.

and how it affects are

studied in physics.

Identify the field of physical science to which each of the following descriptionsbelongs by writing physics or chemistry in the space provided.

_______________________ 6. how a compass works

_______________________ 7. why water boils at 100°C

_______________________ 8. how chlorine and sodium combine to form table salt

_______________________ 9. why you move to the right when the car you are inturns left

Directed Reading A

Name Class Date

Skills Worksheet

DIRECTED READING B

Section: ExploringTHAT’S SCIENCE!

1. How did James Czarnowski get his idea for the penguin boat, Proteus?Explain.

2. What is unusual about the way that Proteus moves through the water?

MATTER + AIR ➔ PHYSICAL SCIENCE

3. What do air, a ball, and a cheetah have in common?

Directed Reading B

Name Class Date

Skills Worksheet

Section: UniqueVOCABULARY

In your own words, write a definition of the following term in the space provided.

1. scientific method

2. technology

3. observation

Name Class Date

Vocabulary & NotesSkills Worksheet

Name Class Date

ReinforcementSkills Worksheet

The Plane TruthComplete this worksheet after you finish reading the Section: [Unique SectionTitle]

You plan to enter a paper airplane contest sponsoredby Talkin’ Physical Science magazine. The personwhose airplane flies the farthest wins a lifetime sub-scription to the magazine! The week before the con-test, you watch an airplane landing at a nearbyairport. You notice that the wings of the airplane haveflaps, as shown in the illustration at right. The paperairplanes you’ve been testing do not have wing flaps.What question would you ask yourself based on these observations? Write yourquestion in the space below for “State the problem.” Then tell how you could usethe other steps in the scientific method to investigate the problem.

1. State the problem.

2. Form a hypothesis.

3. Test the hypothesis.

4. Analyze the results.

5. Draw conclusions.

Flaps


CRITICAL THINKING

A Solar Solution

Name Class Date

Critical Thinking Skills Worksheet

Joseph D. Burns

Inventors’ Advisory Consultants

Portland, OR 97201

Dear Mr. Burns,I’ve got this great idea for a new product called the BlissHeater. It’s a portable, solar-powered space heater. The heater’s design includes these features:•T

he heater will be as longas an adult’s arm and aswide as a

packing box.

•T

he heater will have aglass top set at an angleto catch the sun’s rays.

•T

he inside of the heaterwill be dark colored toabsorb solar heat.If you think my idea will work, I will make the Bliss

Heaters right away without wasting time and money on test-ing and making models. Please write back soon with youropinion.

SECTION REVIEW

Section: UniqueKEY TERMS

1. What do paleontologist study?

2. How does a trace fossil differ from petrified wood?

3. Define fossil.

UNDERSTANDING KEY IDEAS

Name Class Date

Section ReviewSkills Worksheet


[UniqueMULTIPLE CHOICE


______ 1. Surface currents are formed by a. the moon’s gravity. c. wind.b. the sun’s gravity. d. increased water density.

______ 2. When waves come near the shore, a. they speed up. c. their wavelength increases.b. they maintain their speed. d. their wave height increases.

______ 3. Longshore currents transport sediment a . out to the open ocean. c. only during low tide.b. along the shore. d. only during high tide.

______ 4. Which of the following does NOT control surface currents?a. global wind c. Coriolis effectb. tides d. continental deflections

______ 5. Whitecaps break a. in the surf. c. in the open ocean.b. in the breaker zone. d. as their wavelength increases.

______ 6. Most ocean waves are formed by a . earthquakes. c. landsides.b. wind. d. impacts by cosmic bodies.

______ 7. Which factor controls surface currents? a. global winds c. continental deflectionb. the Coriolis effect d. all of the above

______ 8. Streamlike movments of ocean water far below the surface arecalleda. jet currents c. surface currents.b. Coriolis currents. d. deep currents.

______ 9. When the sunlit part of the moon that can be seen from Earthgrows larger, it is a. waxing. c. in the new moon phase.b. waning. d. in the full moon phase.

______10. The Milky Way is thought to be a. an elliptical galaxy. c. a spiral galaxy.

Name Class Date

Chapter Test BAssessment


READING

Read the passages below. Then, read each question that follows the passage.Decide which is the best answer to each question.

Passage 1 adventurous summer camp in the world. Billy can’twait to head for the outdoors. Billy checked the recommendedsupply list: light, summer clothes; sunscreen; rain gear; heavy,down-filled jacket; ski mask; and thick gloves. Wait a minute! Billythought he was traveling to only one destination, so why does heneed to bring such a wide variety of clothes? On further investiga-tion, Billy learns that the brochure advertises the opportunity to“climb the biomes of the world in just three days.” The destinationis Africa’s tallest mountain, Kilimanjaro.

______ 1. The word destination in this passage means A camp B vacation.C place. D mountain.

______ 2. Which of the following is a FACT in the passage? F People ski on Kilimanjaro.G Kilimanjaro is Africa’s tallest mountain.H It rains a lot on Kilimanjaro.J The summers are cold on Kilimanjaro.

______ 3. Billy wondered if the camp was advertising only one destination afterhe read the brochure, which said thatA the camp was the most adventurous summer camp in the world. B he would need light, summer clothes and sunscreen.C he would need light, summer clothes and a heavy, down-filled

jacket.D the summers are cold on Kilimanjaro.

Name Class Date

Standardized Test PreparationAssessment

PERFORMANCE-BASEDASSESSMENT

OBJECTIVEDetermine which factors cause some sugar shapes to break down faster than others.

KNOW THE SCORE!As you work through the activity, keep in mind that you will be earning a gradefor the following:

• how you form and test the hypothesis (30%)

• the quality of your analysis (40%)

• the clarity of your conclusions (30%)

ASK A QUESTIONSWhy do some sugar shapes erode more rapidly than others?

MATERIALS AND EQUIPMENT

Name Class Date

Performanced-Based AssessmentAssessment SKILL BUILDER

Using Scientific Methods

• 1 regular sugar cube • 90 mL of waterCopyright © by Holt, Rinehart and Winston. All rights reserved.

USING VOCABULARY

1. Define biome in your own words.

2. Describe the characteristics of a savanna and a desert.

3. Identify the relationship between tundra and permafrost.

4. Compare the open-water zone and the deep-water zone.

5. Use each of the following terms in an original sentence: plankton, littoralzone, and estuary.

6. Describe how marshes and swamps differ.

Name Class Date

Chapter ReviewSkills Worksheet

SCIENCE PUZZLERS, TWISTERS & TEASERS

CHAPTER TEST A






______ 4. Which of the following does NOT control surface currents?a global wind c Coriolis effect

Name Class Date

Chapter Test AAssessment

CHAPTER TEST C






______ 4. Which of the following does NOT control surface currents?a global wind c Coriolis effect

Name Class Date

Chapter Test CAssessment

For a preview of available worksheets covering math and science skills, see pages T26–T33. All of these resources are also on the One-Stop Planner®.

TEACHER-LED DEMONSTRATION

DEMO

46

Purpose

As students observe the effect of seltzerwater on raisins, they learn about com-bined relative density.

Time Required

10–15 minutes

What to Do

1. Fill the jar or glass with water. Drop aseltzer tablet into the water, and thendrop the raisins in the water. Ask stu-dents to observe what happens to theraisins.

2. Continue observing the behavior of theraisins for a few minutes. Again, askstudents to describe their observations.(The raisins rise to the surface after a shorttime and then sink again. This processcontinues as long as the water fizzes.)

3. Ask students to predict whether theraisins would exhibit the same behaviorwithout the seltzer tablet. Empty theglass or jar and refill it with water. Dropthe raisins into the water. Ask students:What happens? (Without the seltzertablet, the raisins sink to the bottom of thejar and stay there.)

Explanation

The density of the raisins does not change.However, the carbon dioxide bubbles thatadhere to a raisin’s surface cause a muchlower combined density of the raisin andbubbles. The bubbles add little mass to theraisin, but they displace an additional vol-ume of water, causing the raisins withbubbles attached to them to float.

Discussion

Use the following questions as a guide toencourage class discussion:

• What was the purpose of the seltzertablet? (The tablet provided the bubblesthat caused the raisins to rise and sink.)

• Water is denser than carbon dioxide butless dense than a raisin. How can thisstatement be used to explain the behaviorof the raisins? (A raisin by itself is denserthan water and therefore sinks, but a raisincovered with many carbon dioxide bubblesrises. This is because the combined density ofthe raisin and carbon dioxide bubbles is lessthan the density of water. At the surface,some of the bubbles burst. When this hap-pens, the combined density of the raisin andcarbon dioxide bubbles increases, and theraisin begins to sink again.)

• Critical Thinking Use what you haveobserved in this activity to explain howa lava lamp works. (As the wax reachesthe warm light, its density decreases andthe wax rises. As it floats away from theheat source, the wax cools and condenses.The density increases and the wax sinksagain.)

The Rise and Fall of Raisins

MATERIALS

• large, tall transparent jar or glass• 5–10 raisins• seltzer tablet• tap water

Brian BurnightBig Bear Lake Middle School

Big Bear Lake, California

TEACHER PREP

CONCEPT LEVEL

CLEAN UP

E A S Y H A R D

Lab Ratings

Chapter 7 • Chapter Resources 177D

WHIZ-BANGDEMONSTRATIONS

TEACHER-LED DEMONSTRATION

DEMO

47

Going Against the FlowPurpose

Students learn how air pressure affects theflow of fluids.

Time Required

5–10 minutes

sors or a nail to puncture a small holein the side of the bottle, close to thebottom. Ask students: What will hap-pen when I fill the bottle with water?(Expected answer: Water will come out ofthe hole at the bottom of the bottle.)

2. Holding the bottle over a bucket orsink, fill the bottle with water. Keep thestopper unplugged, and while the waterstreams out of the bottle, ask students:How can I stop the stream of waterwithout getting wet? (Expected answer: Itis impossible.)

3. Tell students that it’s possible to stopthe stream without touching it. Thenplug the hole in the stopper at themouth of the bottle. The water willstop flowing from the bottle.

Discussion

Use questions such as the following to en

MATERIALS

• plastic bottle• one-hole stopper that fits snugly into the

plastic bottle• scissors or a nail• bucket or sink• tap water

TEACHER PREP

CONCEPT LEVEL

CLEAN UP

E A S Y H A R D

Lab Ratings

What’s the Flap All About?

STUDENT WORKSHEET

FIELD ACTIVITY

18

PH

YSIC

AL S

CIE

NC

E

▼▼▼

Name Date Class

It’s not easy working for a genius . . .Your tutor, Leonardo DaVinci, is hatching another scheme. He

has this wild idea that a human can fly like a bird. Imagine that!Unfortunately, this preoccupation with flight has stopped all ofhis other work. He cannot even pick up a piece of paper withoutfolding it into a birdlike shape and sailing it through the air.How can humans fly without feathers? Has DaVinci lost hismind?

Now DaVinci is designing a flying machine, and he has askedyou for help. You must go out into the field and observe birds as they take flight,soar, rise, dive, and land. Is it possible that studying these amazing creaturescould unlock the secrets of flight? Master DaVinci seems to think so.

Objective Observe birds as they fly, paying careful attention to the size,shape, angle, and movement of the wings and tail; and useyour observations to design a paper airplane that will glide far-ther than your classmates’ planes.

Look Up in the Sky!1. Your teacher will tell you where and when you can watch

birds fly. A pair of binoculars and a field guide will help youwith your observations.

2. At the designated place and time, watch a bird fly for 10–15minutes. In your ScienceLog, describe the size, shape, angle,and movement of a bird’s wings and tail. If you have a fieldguide, use it to identify the bird. Sketch the bird’s body as it flies.

3. In your ScienceLog, use your sketch of the bird to draw a paper-airplane design.

4. In your ScienceLog, illustrate the forces that act on the bird.Draw arrows indicating the direction of each force. Usingthe terms at left, explain how these forces affect the bird asit flies. Remember, air is a fluid!

5. Use your ScienceLog drawing to build a paper airplane thatwill fly farther that your classmates’ planes. Pay careful attention to the shape and size of the wing and tail. Youmay cut and paste the paper—you do not have to rely onfolding.

6. When your teacher gives you the signal, line up and fly yourplanes. Whose plane flew the farthest? In your ScienceLog,describe how their design was different from yours.

MATERIALS

• binoculars (optional)• field guide to birds• paper• scissors• tape• glue

SAFETY ALERT!

Go with an adult to ob-serve bird flight. Do notgo alone.

USEFUL TERMS

gravitydownward forceliftupward forcethrustforward forcedragbackward force

Name ___________________________________________________ Date _________________ Class _____________

PROJECT

STUDENT WORKSHEET57

Scuba Dive

You take a deep breath, adjust your mask, put your regulator in your mouth, andtip over backward off the boat. With a splash, you enter the warm, blue water.Your own breathing sounds loud in your ears as you descend slowly. Brilliantly col-ored tropical fish swim past you, your ears clear, and you find yourself at home in the world beneath the waves.

Under the Sea1. Many forces relating to water limit undersea exploration.

Research the sport of scuba diving. What equipment wasused before the invention of scuba gear? When was scubagear invented? Find out what changes have been madesince scuba diving first came about. What are the proper-ties of fluids that can make diving hazardous? Write anarticle for your school newspaper about the science behindscuba. Using your research and what you know aboutforces in fluids explain the precautions scuba divers musttake to ensure a safe dive. Be sure to include a descriptionof the health risks of diving to great depths and howdivers control their buoyancy.

Another Research Idea2. The first submarines were little more than hollowed-out

iron cylinders. After World War II, great advances weremade in submarine technology. What kinds of materialsare used in submarines today? How are modern sub-marines different from the early submarines? How are sub-marines designed to withstand the pressures of deep seasubmersion? How are submarines designed to take advan-tage of forces in the water? Make a poster of different submarine designs or a cut-away model of a sub and pre-sent your research to the class.

Long-Term Project Idea3. Until 1999, many people attempted to go around the

world in a hot air balloon, and all of them failed. Whatmade the difference in 1999? What kinds of hot air bal-loons were being used? What were the most commonproblems faced by would-be circumnavigators, people whotravel around the world? When were hot air balloons first invented? How have balloon designs changed overthe years? Design a new hot air balloon, and create a mar-keting brochure to attract a fictional sponsor. In thebrochure, you will need to point out the strengths of yourdesign and explain why it is better than previous balloonsthat failed.

Under Pressure2. Becky Beaker has a very adventurous robot. To keep track of her

roaming robot, she has attached a device that will measure atmos-pheric pressure. The table at the bottom of this page indicates theapproximate pressure of air at various locations where her robotmight be found.

Using the questions below, you can determine the atmosphericpressure where Becky’s robot is currently located. Begin with thefirst statement and decide if it is true or false. If it is true, circle themathematical expression under the True column, and vice-versa.Then follow the directions that you have circled. The atmosphericpressure you end up with will guide you to the robot.

True False

a. Liquids are fluids, but start with start with 2 kPagases are not. 3 kPa

b. Liquids generally cannot multiply add 6be compressed as much as by 12gases, making liquids ideal

Name _______________________________________________ Date ________________ Class______________

SCIENCE PUZZLERS, TWISTERS & TEASERS7

Forces in Fluids

CHAPTER

Copyright © by Holt, Rinehart and Winston. All rights reserved.Copyright © by Holt, Rinehart and Winston. All rights reserved.


Name Class Date

Reaction to StressQuick Lab DATASHEET FOR QUICK LAB

BackgroundThe graph below illustrates changes that occur in the membrane potential of aneuron during an action potential. Use the graph to answer the followingquestions. Refer to Figure 3 as needed.

Analysis1. Determine about how long an action potential lasts.

2. State whether voltage-gated sodium, chanels are open or closed at point A.

3. State whether voltage-gated potassium channels are open or closed atpoint B.

4. Critical Thinking Recognizing Relationships What causes the menberneotential to become less negative at point A?

5. Critical Thinking Recognizing Relationships What causes the membranepotential to become more negative at point B?


Answer here.

Answer here.

Answer here.

Answer here.

Answer here.

Using Scientific Methods

GENERAL

GENERAL

SPECIAL NEEDS

GENERAL GENERAL

GENERAL

GENERAL

GENERAL

GENERAL

GENERAL SPECIAL NEEDS

GENERAL

GENERAL

SAMPLE

SAMPLE SAMPLE

SAMPLE SAMPLE

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SAMPLE

SAMPLESAMPLE

SAMPLE

SAMPLE

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SAMPLE

DATASHEETS FORCHAPTER LABS

Teacher’s NotesTIME REQUIRED

One 45-minute class period.

RATINGTeacher Prep–3Student Set-Up–2Concept Level–2Clean Up–2

MATERIALS

The materials listed on the student page are enough for a group of 4–5 students.Large, dried beans of any kind will work well in this exercise.

SAFETY CAUTION

Remind students to review all safety cautions and icons before beginning this labactivity.

Using Scientific MethodsSkills Practice Lab DATASHEET FOR CHAPTER LAB


1 2 3 4Easy Hard

Jason MarshMontevideo High

and Country School

SAMPLE

DATASHEETS FORLABBOOK

Teacher’s NotesTIME REQUIRED

One 45-minute class period.

Does It All Add Up?Skills Practice Lab DATASHEET FOR LABBOOK LAB


Jason MarshMontevideo High

SAMPLE

Chapter Enrichment

This Chapter Enrichment provides relevant and

interesting information to expand and enhance

your presentation of the chapter material.

Fluids and PressureRefresher on Gas Laws• Nearly all materials expand

when they are heated and contract when they are cooled. Gases are not an exception. A gas expands as it gets hotter because the kinetic energy of its particles increases. When the kinetic energy increases, the particles move faster and bounce against each other harder. This movement causes the gas particles to move far-ther apart, and the gas expands. If the pressure does not change, the volume of the gas will increase as the temperature increases. This property of gases is known as Charles’s law.

• The air pressure inside the tires of an automobile can be much greater than the pressure outside the tires. The pressure can be greater inside an enclosed con-tainer because air, like all gases, is compressible. If the temperature does not change, the pressure of a gas will increase as the volume decreases. This property of gases is known as Boyle’s law.

Is That a Fact!◆ The water pressure at the bottom of a small, deep

pond is greater than the pressure at the bottom of a large, shallow lake because water pressure is deter-mined by the depth of the water, not the volume of the water.

Buoyant ForceArchimedes (287–212 BCE)• Archimedes, a Greek mathematician, inventor, and

physicist, lived in the ancient city of Syracuse from 287 to 212 BCE. He is famous for his work in geom etry, physics, mechanics, and water pressure.

Diving and Water Pressure• Scuba diving relies in part on the principles of buoy-

ancy and fluid pressure. Some of the effects of water pressure can be felt even in a swimming pool. Just a few meters under water, your ears begin to hurt from the pressure of the water on your eardrums.

• As a diver descends deeper into the water with scuba gear, the diver’s lungs hold more air because the air is compressed by the water pressure. As a diver rises to the surface, the air expands again. Under certain cir-cumstances, the air in a diver’s lungs could expand enough to rupture the air sacs in the diver’s lungs.

Is That a Fact!◆ Humans have built underwater vessels for hundreds

of years. In 1620, the Dutch inventor Cornelis Drebbel built what is thought to be the first submarine. His vessel was not much more than a rowboat covered with greased leather. It traveled at a depth of 4 to 5 m under water in the Thames River, in London, England. King James I of England is said to have taken a short ride in this vessel.

Neutral Buoyancy• Scuba divers use weights to compensate for the buoy-

ancy of their body and diving gear. When a diver weighs exactly the same as an equal volume of the sur-rounding water, the diver can swim to any depth and remain there effortlessly. This state is called neutral buoyancy.

177E Chapter 7 • Forces in Fluids

7

Fluids and MotionDaniel Bernoulli (1700 –1782)• Daniel Bernoulli was born in the Netherlands in 1700.

For most of his life, he lived in Basel, Switzerland.

• Bernoulli was born into a family distinguished for accomplishments in science and mathematics. His father, Johann, was famous for his work in calculus, trigonometry, and the study of geodesics. Bernoulli’s uncle Jacob was integral in the development of calcu-lus. Bernoulli’s brothers, Nicolaus and Johann II, were also noted mathematicians and physicists.

• Bernoulli’s greatest work was Hydrodynamica, which was published in 1738. It included the concept now known as Bernoulli’s principle. He also made important contributions to probability theory and studied astronomy, botany, physiology, gravity, and magnetism.

Examples of Bernoulli’s Principle• Even on a calm night, air moves across the top of a

chimney. This air movement causes the pressure at the top of the chimney to be lower than the pressure in the house. According to Bernoulli’s principle, the smoke in the fireplace is pushed up the chimney by the greater air pressure in the house.

• Bernoulli’s principle also explains why a soft convert-ible top on a car bulges when the car travels at high speeds. The air moving over the top causes an area of low pressure, and the higher pressure inside the car pushes the soft top up.

Is That a Fact!◆ Water flowing in a stream speeds up when it flows

through a narrow part of the stream bed. According to Bernoulli’s principle, the water pressure decreases as the speed increases.

Blaise Pascal• Blaise Pascal (1623–1662) was a famous French scien-

tist, mathematician, philosopher, and writer of prose. He had no formal schooling but pursued his interests under his father’s guidance. Pascal’s father forbade him to study mathematics until he was 15 years old, but Pascal’s curiosity led him to begin studying geom-etry in secret at the age of 12. By the time he was 14, Pascal was regularly attending sessions with the lead-ing ge ometricians of his time. Pascal presented his first mathematics paper at the age of 16. The SI unit for pressure, the pascal, is named after Blaise Pascal.

For background information about teaching strategies and

issues, refer to the Professional Reference for Teachers.

Topic: Fluids and PressureSciLinks code: HSM0586

Topic: Buoyant ForceSciLinks code: HSM0202

Topic: Bernoulli’s PrincipleSciLinks code: HSM0143

Visit www.scilinks.org and enter the SciLinks code for more information about the topic listed.

Developed and maintained by theNational Science Teachers Association

SciLinks is maintained by the National Science Teachers Association to provide you and your students with interesting, up-to-date links that will enrich your classroom presentation of the chapter.

Chapter 7 • Chapter Enrichment 177F

Standards Correlations

National Science Education Standards

The following codes indicate the National Science EducationStandards that correlate to this chapter. The full text of thestandards is at the front of the book.

Chapter OpenerSAI 1, 2; ST 2

Section 1 Fluids and PressureSAI 1; ST 2; PS 1a

Section 2 Buoyant ForceSAI 1; ST 2; HNS 3; PS 1a, 2c; LabBook: SAI 1

Section 3 Fluids and MotionUCP 5; SAI 1; ST 2; SPSP 5; HNS 3; LabBook: SAI 1

Chapter LabSAI 1

Chapter ReviewSAI 1

Science in ActionSPSP 5

OverviewTell students that this chapterwill help them learn about fluidsand the forces caused by fluids,including buoyant force, lift,and drag. Students also learnabout pressure and the factorsthat affect flight.

Assessing PriorKnowledgeStudents should be familiarwith the following topics:

• forces and net force

• motion and speed

• SI units

IdentifyingMisconceptionsAs students learn the material inthis chapter, some of them mayhave difficulties understandingthat gases, such as oxygen andair, are fluids. This confusionmay result from the commonusage of the word fluid. In every-day language, fluids usually referto liquids only.

7

178 Chapter 7 • Forces in Fluids

PRE-READINGPRE-READING

Forces in Fluids

About the

As you race downhill on your bicycle, the airaround you pushes on your body and slowsyou down. “What a drag!” you say. Well,actually, it is a drag. When designing bicyclegear and clothing, manufacturers considermore than just looks and comfort. They alsotry to decrease drag, a fl uid force that opposesmotion. This photo shows cyclists riding theirbikes in a wind tunnel in a study of how afl uid—air—affects their ride.

Booklet Before you readthe chapter, create theFoldNote entitled “Booklet”

described in the Study Skills sectionof the Appendix. Label each page ofthe booklet with a main idea from thechapter. As you read the chapter, writewhat you learn abouteach main idea on theappropriate page of thebooklet.

SECTION

Forces in fl uids are relatedto pressure and density andcan affect the motion ofobjects in the fl uid.

7

1 Fluids and Pressure . . . . . . . . . 180

2 Buoyant Force . . . . . . . . . . . . . 186

3 Fluids and Motion . . . . . . . . . . 192

START-UPTaking FlightIn this activity, you will build a model airplane to learn how wing size affects flight.

Procedure1. Fold a sheet of paper in half lengthwise. Then,

open it. Fold the top corners toward the center crease. Keep the corners folded down, and fold the entire sheet in half along the center crease.

2. With the plane on its side, fold the top front edge down so that it meets the bottom edge. Fold the top edge down again so that it meets the bottom edge. Turn the plane over, and repeat.

3. Raise the wings so that they are perpendicular to the body.

4. Point the plane slightly upward, and gently throw it. Repeat several times. Describe what you see.

5. Make the wings smaller by folding them one more time. Gently throw the plane. Repeat several times. Describe what you see.

6. Using the smaller wings, try to achieve the same flight path you saw when the wings were bigger.

Analysis1. What happened to the plane’s flight when you

reduced the size of its wings? What did you have to do to achieve the same flight path as when the wings were bigger?

2. What gave your plane its forward motion?

START-UPSTART-UP vvM A T E R I A L S

FOR EACH STUDENT• paper, sheet

Teacher’s Notes: Tell students that this activity is an exception to the usual rules about flying paper planes in class.

Answers

1. Sample answer: The plane did not stay in the air as long. To get a longer flight, I had to throw much harder.

2. Sample answer: I gave the plane its forward motion when I threw the plane.

��

� �

A

��

��

B

F

C

�

E

�

D

�

�Forces in Fluids CHAPTER STARTER

You’re the pilot of a revolutionary newundersea vessel, Deep Flight, and todayis the day of your first undersea voyage.Your destination: the Mariana Trench,which is the deepest spot in the ocean.The Mariana Trench is about 11 kmdeep—that’s deep enough toswallow Mount Everest, thetallest mountain in theworld. Fewer than a dozenundersea vessels have everventured this far down. Thereason? Water exertstremendous pressure at thisdepth. Luckily, Deep Flight’shull is made of an extremelystrong ceramic material that can with-stand the pressure.

What makes Deep Flight so revolu-tionary? Deep Flight actually “flies”through the water. In fact, Deep Flightlooks a lot like an airplane with stubbywings. Controls allow you to adjust thecurvature of the wings to move fasterthrough the water.

With its battery-powered motor and yourability to change the curvature of the wings,Deep Flight can reach speeds of up to 25 km/h! By adjusting Deep Flight’s wingflaps and tail fins, you can do dives, spins,and turns. Ready to race a whale?

As futuristic as this story sounds, DeepFlight is a real undersea vessel that iscurrently being tested. Although DeepFlight has not yet made it to the bottomof the Mariana Trench, some scientistsbelieve this type of undersea vessel willone day be used routinely to explore theocean floor.

In this chapter you will explore flu-ids. You’ll learn how pressure is exertedby water and other fluids. You’ll also learnwhy some things sink and others float.Dive in!


Imagine . . .

Chapter Starter TransparencyUse this transparency to help students begin thinking about fluids and pressure.

CHAPTER RESOURCESTechnology

Transparencies • Chapter Starter Transparency

Student Edition on CD-ROM

Guided Reading Audio CD • English or Spanish

Classroom Videos • Brain Food Video Quiz

Workbooks

Science Puzzlers, Twisters & Teasers • Forces in Fluids g

READINGSKILLS

Chapter 7 • Forces in Fluids 179

READING STRATEGY

Fluids and PressureWhat does a dolphin have in common with a sea gull? What does a dog have in common with a fl y? What do you have in common with all these living things?

One answer to these questions is that you and all these otherliving things spend a lifetime moving through fluids. A fluidfluid isany material that can flow and that takes the shape of itscontainer. Fluids include liquids and gases. Fluids can flowbecause the particles in fluids move easily past each other.

Fluids Exert PressureYou probably have heard the terms air pressure and waterpressure. Air and water are fluids. All fluids exert pressure. So,what is pressure? Think about this example. When you pumpup a bicycle tire, you push air into the tire. And like all matter,air is made of tiny particles that are constantly moving.

Look at Figure 1. Inside the tire, the air particles collidewith each other and with the walls of the tire. Together, thesecollisions create a force on the tire. The amount of force exertedon a given area is pressure.pressure.

Calculating PressurePressure can be calculated by using the following equation:

The SI unit for pressure is the pascal.pascal. One pascal (1 Pa) isthe force of one newton exerted over an area of one squaremeter (1 N/m2).

Figure 1 The force of the air particles hitting the inner surface of the tire creates pressure, which keeps the tire inflated.

fluidfluid a nonsolid state of matter in which the atoms or molecules are free to move past each other, as in a gas or liquid

pressurepressure the amount of force exerted per unit area of a surface

pascalpascal the SI unit of pressure (symbol, Pa)

atmospheric pressureatmospheric pressure thepressure caused by the weight of the atmosphere

areapressure �force

1What You Will Learn

Describe how fluids exert pressure.Analyze how atmospheric pressurevaries with depth.Explain how depth and density affectwater pressure.Give examples of fluids flowing fromhigh to low pressure.

Vocabularyfluidpressurepascalatmospheric pressure

Brainstorming The key idea of thissection is pressure. Brainstorm wordsand phrases related to pressure.

1

OverviewIn this section, students learnabout the properties of fluids.Students also learn how pressureis related to depth and densityand how fluids flow from areasof high pressure to areas of lowpressure.

BellringerHave your students imagine thefollowing situation: “One after-noon, you go outside to findyour younger sister standing byher bike holding a nail in herhand. The bike has a flat tire.She wants to know why the aircame out of the tire when shepulled the nail out.” Have stu-dents write a few sentences toexplain why air rushes out of ahole in a tire.

MISCONCEPTIONALERT

Pressure and WeightStudents might assume thatpressure calculations willalways involve the force of afluid. Explain that becauseweight is a measure of gravi-tational force, anything thathas weight exerts pressure.Thus, a crate on a floor exertspressure on the floor.

CHAPTER RESOURCES

Chapter Resource File

CRF • Lesson Plan• Directed Reading Ab, Bs

Technology

Transparencies• Bellringer• LINK TOLINK TO LIFE SCIENCELIFE SCIENCE L6 Math Focus: Surface

Area-to-Volume Ratio

Workbooks

Interactive Textbook Struggling Readers Struggling Readers

Math Skills for Science• The Pressure Is On!g

Is That a Fact!The air in a large room in your houseweighs about as much as an averageadult male (about 736 N)!


Pressure and BubblesWhen you blow a soap bubble, you blow in onlyone direction. So, why does the bubble get rounderinstead of longer as you blow? The shape of thebubble partly depends on an important property offluids: Fluids exert pressure evenly in all directions.The air you blow into the bubble exerts pressureevenly in all directions. So, the bubble expands inall directions to create a sphere.

Atmospheric PressureThe atmosphere is the layer of nitrogen, oxygen, andother gases that surrounds Earth. Earth’s atmosphereis held in place by gravity, which pulls the gasestoward Earth. The pressure caused by the weight ofthe atmosphere is called atmospheric pressure.

Atmospheric pressure is exerted on everythingon Earth, including you. At sea level, the atmo-sphere exerts a pressure of about 101,300 N onevery square meter, or 101,300 Pa. So, there is aweight of about 10 N (about 2 lbs) on every squarecentimeter of your body. Why don’t you feel thiscrushing pressure? Like the air inside a balloon,the fluids inside your body exert pressure. Figure 2can help you understand why you don’t feel thepressure.

✓Reading Check Name two gases in the atmosphere.(See the Appendix for answers to Reading Checks.)

Figure 2 The air inside a balloon exerts pressure that keeps the balloon inflated against atmospheric pressure. Similarly, fluid inside your body exerts pressure that works against atmospheric pressure.

Pressure, Force, and Area What is the pressureexerted by a book that has an area of 0.2 m2

and a weight of 10 N?

Step 1: Write the equation for pressure.

Step 2: Replace force and area with the valuesgiven, and solve. (Hint: Weight is ameasure of gravitational force.)

The equation for pressure can be rearrangedto find force or area, as shown below.

Now It’s Your Turn1. Find the pressure exerted by a 3,000 N

crate that has an area of 2 m2.2. Find the weight of a rock that has an area

of 10 m2 and that exerts a pressure of250 Pa.

pressure �forcearea

pressure � � 50 N/m2 � 50 Pa10 N

0.2 m2

area � pressureforce

force � pressure � area (Rearrange by multiplying by area.)

(Rearrange by multiplying by area and then dividing by pressure.)

Atmosphericpressure

Air pressure inside the balloon

Demonstration --------------gSafety Caution: Have studentswear protective goggles duringthis demonstration.

Building Pressure Place twoplastic soda bottles filled half-way with water in front of theclassroom. Add some fizzingpowder or crushed fizzing tab-lets to each bottle. Immediately,place a cork snugly in one of thebottles. Stretch the mouth of aballoon over the other bottle,sealing the opening of the bot-tle. Have the class observe whathappens. Ask students to explainwhat happened in each bottle.(Sample answer: The fizzing tabletcreated gas. The gas created pres-sure inside the bottle with the cork,and the pressure forced the corkoff. The balloon on the other bottlewas filled by the gas created by thetablet.) l Visual

CONNECTIONCONNECTION vvLanguage Arts -------------------g

Writing Fluid Poem Have stu-dents write a short poemdescribing something

about fluids. Some possibletopics include water, mixingliquids, air, steam, clouds, orfog. l Verbal

h-----------------------------a

Comparing Pressure Have stu-dents calculate the pressureexerted by their bodies on thefloor. Students should estimatethe area of their feet as a rectan-gle. Ask students to compare thepressure exerted when their feetare flat on the floor with thepressure exerted when studentsare standing on their toes.l Logical

Answer to Math Focus

1. pressure � 3,000 N � 2 m2 � 1,500 Pa2. force � 250 Pa � 10 m2 � 2,500 N

Answer to Reading Check

Two gases in the atmosphere are nitrogenand oxygen.

CONNECTION toCONNECTION toLife Science -----------------------------------g

Surface Area-to-Volume Ratio Use theteaching transparency titled “Math Focus:Surface Area-to-Volume Ratio” to help stu-dents understand how objects, includingthe human body, can withstand atmosphericpressure.

Section 1 • Fluids and Pressure 181

Variation of Atmospheric PressureThe atmosphere stretches about 150 kmabove Earth’s surface. However, about80% of the atmosphere’s gases are foundwithin 10 km of Earth’s surface. At thetop of the atmosphere, pressure is almostnonexistent. The pressure is close to 0 Pabecause the gas particles are far apart andrarely collide. Mount Everest in south-central Asia is the highest point on Earth.At the top of Mount Everest, atmosphericpressure is about 33,000 Pa, or 33 kilo-pascals (33 kPa). (Remember that the prefixkilo- means 1,000. So, 1 kPa is equal to1,000 Pa.) At sea level, atmospheric pres-sure is about 101 kPa.

Atmospheric Pressure and DepthTake a look at Figure 3. Notice how atmo-spheric pressure changes as you travelthrough the atmosphere. The further downthrough the atmosphere you go, the greaterthe pressure is. In other words, the pressureincreases as the atmosphere gets “deeper.”An important point to remember aboutfluids is that pressure varies dependingon depth. At lower levels of the atmo-sphere, there is more fluid above that isbeing pulled by Earth’s gravitational force.So, there is more pressure at lower levelsof the atmosphere.

✓✓Reading Check Describe how pressure changes with depth.

Pressure Changes and Your BodySo, what happens to your body whenatmospheric pressure changes? If youtravel to higher or lower points in theatmosphere, the fluids in your body haveto adjust to maintain equal pressure. Youmay have experienced this adjustment ifyour ears have “popped” when you werein a plane taking off or in a car travelingdown a steep mountain road. The “pop”happens because of pressure changes inpockets of air behind your eardrums.

At 150,000 m above sea level, atmospheric pressure is almost 0 Pa. Humans cannot travel this high without protec-tion. The space shuttle travels past this point on its way into orbit.

The atmospheric pres-sure at 12,000 m is about 20 kPa. Airplane cabins must be pressur-ized for passenger safety.

At the top of Mount Everest (8,847 m above sea level), atmospheric pressure is about a third of that at sea level.

Atmospheric pressure at La Paz, Bolivia (the world’s highest capital city, at 4,000 m), is about 51 kPa.

At sea level (0 m), the full pressure of the atmosphere— 101 kPa—is exerted on you.

Differences in Atmospheric PressureFigure 3

CONNECTIONCONNECTION vvEarth Science ----------------------g

Weather and Pressure Havestudents research the effectsof atmospheric pressure onweather. Have students make aposter or concept map to displaytheir results. l Visual

Mount Everest The highaltitude of Mount Everestcan be hazardous to visitors’health. Most of the moun-tain’s base camps are morethan 4,000 m above sea level.Altitude sickness can affectpeople who reach that eleva-tion. Climbers must useoxygen masks above 5,500 mbecause, at that elevation,there is not enough oxygento sustain normal bodyfunctions.

h-----------------------------g

Writing Pressure Essay Havestudents write an essaydescribing how they are

affected by fluid pressure on atypical day. Students shouldinclude examples such asweather, transportation,plumbing, breathing,and so on. l Verbal PORTFOLIO


Pressure increases as depthMISCONCEPTION

ALERT

Variation of Air Density The relation-ship between pressure and depth in theatmosphere is not the same as in theocean. Air is less dense at higher alti-tudes. So, the pressure in the upperatmosphere varies less with depth than

pressure in the lower atmosphere does.But water density in the ocean remainsapproximately constant with depth. So,the rate of change in pressure remainsrelatively constant as you go deeperunderwater.


Water PressureWater is a fluid. So, it exerts pressure likethe atmosphere does. Water pressure alsoincreases as depth increases, as shown inFigure 4. The deeper a diver goes in thewater, the greater the pressure is. Thepressure increases because more waterabove the diver is being pulled by Earth’sgravitational force. In addition, the atmo-sphere presses down on the water, so thetotal pressure on the diver includes waterpressure and atmospheric pressure.

Water Pressure and DepthLike atmospheric pressure, water pressuredepends on depth. Water pressure doesnot depend on the total amount of fluidpresent. A swimmer would feel the samepressure swimming at 3 m below thesurface of a small pond and at 3 m belowthe surface of an ocean. Even thoughthere is more water in the ocean thanin the pond, the pressure on the swimmerin the pond would be the same as thepressure on the swimmer in the ocean.

Density Making a DifferenceWater is about 1,000 times more densethan air. Density is the amount of matterin a given volume, or mass per unit vol-ume. Because water is more dense thanair, a certain volume of water has moremass—and weighs more—than the samevolume of air. So, water exerts morepressure than air.

For example, if you climba 10 m tree, the decrease inatmospheric pressure is toosmall to notice. But if youdive 10 m underwater, thepressure on you increases to201 kPa, which is almost twicethe atmospheric pressureat the surface!

Pressure exerted on a diver 10 m below the water’s surface is twice the pressure at the surface.

At 500 m below the surface, pressure is about 5,000 kPa. Divers at or below this level must wear special suits to survive the pressure.

The wreck of the Titanic is 3,660 m below the surface. The water pressure at this depth is 36,600 kPa.

The viper fishlives 8,000 m below the ocean’s surface. No fishare found below this level. The water pressure at this depth is 80,000 kPa.

In 1960, the Triestedescended to the deepest part of the ocean (11,000 m), where the pressureis 110,000 kPa.

Differences in Water PressureFigure 4 CONNECTION toCONNECTION toReal World -----------------------------------g

Pressure and Diving The pres-sure on a diver’s body increasesas the diver goes deeper under-water. The increased pressure onthe diver’s chest makes breath-ing more difficult. Scuba diversuse a pressure regulator to solvethis problem. As they go deeper,the regulator increases the pres-sure of the air released from thediver’s air tanks. The pressure ofthe released air equals the pres-sure of the water on the diver,making breathing easier.

CulturalAwarenessCulturalAwareness g

Pearl Diving Have studentsresearch Japanese pearl div-ers. Students should investi-gate the techniques thesedeep divers use to cope withthe effects of water pressure.Ask students to make a posterthat illustrates what theylearn. l Visual

StrategiesStrategiesINCLUSIONINCLUSION

• Attention Deficit Disorder• Developmentally Delayed• Hearing ImpairedMany students benefit fromhands-on activities. Givestudents a hands-on opportu-nity to clarify the meaning ofthe word density. Working insmall groups, have studentsgather a kilogram of each ofthe following items: marsh-mallows, popcorn kernels,and measuring masses (themetal “weights” used withtwo-pan balances). Have eachstudent handle the items tofeel their masses and com-pare their volumes. Ask eachgroup to write a paragraphcomparing the volumes andmasses of the different itemsand indicating the order ofthe items from highest tolowest. l Kinesthetic

CHAPTER RESOURCESWorkbooks

Math Skills for Science• Densityg

SUPPORT FOR

English Language LearnersPressure and Depth To check com-prehension of the relationship betweenair pressure and depth as well as waterpressure and depth, ask students tosummarize what they have learnedafter reading the text and the graphicson these pages. Have students write abrief summary explaining how pres-sure changes with depth and what thatmeans for the human body in eachenvironment. Evaluate the summariesbased on accuracy of information, clar-ity of organization, and grammar andspelling.l Verbal


Pressure Differences and Fluid FlowWhen you drink through a straw, you remove some of theair in the straw. Because there is less air inside the straw, thepressure in the straw is reduced. But the atmospheric pressureon the surface of the liquid remains the same. Thus, there is adifference between the pressure inside the straw and the pres-sure outside the straw. The outside pressure forces the liquid upthe straw and into your mouth. So, just by drinking through astraw, you can observe an important property of fluids: Fluidsflow from areas of high pressure to areas of low pressure.

✓Reading Check When drinking through a straw, how do youdecrease the pressure inside the straw?

Pressure Differences and BreathingTake a deep breath—fluid is flowing from high to low pressure!When you inhale, a muscle increases the space in your chestand gives your lungs room to expand. This expansion decreasesthe pressure in your lungs. The pressure in your lungs becomeslower than the air pressure outside your lungs. Air then flowsinto your lungs—from high to low pressure. This air carriesoxygen that you need to live. Figure 5 shows how exhaling alsocauses fluids to flow from high to low pressure. You can seea similar flow of fluid when you open a carbonated beverageor squeeze toothpaste onto your toothbrush.

Exhaling, Pressure, and Fluid FlowFigure 5

Blown Away1. Lay an empty plastic soda

bottle on its side.2. Wad a small piece of

paper (about 4 � 4 cm)into a ball.

3. Place the paper ball justinside the bottle’s opening.

4. Blow straight into theopening.

5. Record your observations.6. Explain your results in

terms of high and lowfluid pressures.

When you exhale,a muscle in yourchest moves up-ward and decreasesthe space in yourchest.

a

The decrease in spacecauses the pressure inyour lungs to increase.The air in your lungsfl ows from a regionof high pressure (yourchest) to a region oflow pressure (outsideof your body).

b

Exhaled air carriescarbon dioxide outof the lungs.

c

Reteaching -------------------------------------bHow Droppers Work Giveeach pair of students a plasticdropper and a small cup ofwater. Ask students to write aparagraph describing how thedropper works. Students shouldaddress why water goes up intothe dropper and why the watercan be forced out. Students mayexperiment with the droppers asthey write their paragraphs.(Both events can be explained bythe fact that fluids flow from areasof high pressure to areas of lowpressure.) l Verbal/Kinesthetic

Quiz --------------------------------------------------------------------g

1. What do liquids and gaseshave in common? (They areboth fluids.)

2. Why does pressure increasewith depth? (As depthincreases, the weight of thefluid above increases, whichincreases pressure.)

AlternativeAssessment ---------------------------a

Airflow Tracking Have studentsmake a poster showing the air-flow in their home. Have themwrite a short description of thecirculation of the air by usingthe concept of fluid pressure.Students should also describehow they tracked the airflowin their home. l Visual


You decrease pressure inside astraw by removing some of the airinside the straw.

M A T E R I A L SFOR EACH STUDENT

• bottle, soda, plastic• paper, 4 � 4 cm square

Answers

5. Students should observe that the paper wadflies out of the bottle.

6. By blowing into the bottle, one increasesthe air pressure inside the bottle. Fluidsflow from high pressure to low pressure,so the air inside flows out of the bottleand carries the paper wad with it.


For a variety of links related to thischapter, go to www.scilinks.org

SummarySummary

Review

Pressure Differences and TornadoesLook at the tornado in Figure 6. Some of thedamaging winds caused by tornadoes are the resultof pressure differences. The air pressure inside atornado is very low. Because the air pressure outsideof the tornado is higher than the pressure inside, airrushes into the tornado. The rushing air causes thetornado to be like a giant vacuum cleaner—objectsare pushed into the tornado. The winds created areusually very strong and affect the area around thetornado. So, objects, such as trees and buildings,can be severely damaged by wind even if they arenot in the direct path of a tornado.

• A fluid is any materialthat flows and takes theshape of its container.

• Pressure is force exertedon a given area.

• Moving particles ofmatter create pressureby colliding with oneanother and with thewalls of their container.

• The pressure causedby the weight of theatmosphere is calledatmospheric pressure.

• Fluid pressure increasesas depth increases.

• As depth increases,water pressure increasesfaster than atmosphericpressure does becausewater is denser than air.

• Fluids flow from areas ofhigh pressure to areas oflow pressure.

Using Key Terms

1. In your own words, write a defi-nition for each of the followingterms: fluid and atmosphericpressure.

2. Use the following terms in thesame sentence: pressure andpascal.

Understanding Key Ideas

3. Which of the followingstatements about fluids is true?

a. Fluids rarely take the shape oftheir container.

b. Fluids include liquids andgases.

c. Fluids flow from low pressureto high pressure.

d. Fluids exert the most pressurein the downward direction.

4. How do fluids exert pressure ona container?

5. Why are you not crushed byatmospheric pressure?

6. Explain why atmospheric pres-sure changes as depth changes.

7. Give three examples of fluidsflowing from high pressure tolow pressure in everyday life.

Math Skills

8. The water in a glass has a weightof 2.4 N. The bottom of the glasshas an area of 0.012 m2. What isthe pressure exerted by the wateron the bottom of the glass?

Critical Thinking

9. Identifying RelationshipsMercury is a liquid that has adensity of 13.5 g/mL. Water hasa density of 1.0 g/mL. Equal vol-umes of mercury and water arein identical containers. Explainwhy the pressures exerted on thebottoms of the containers aredifferent.

10. Making Inferences Why doairplanes need to be pressurizedfor passenger safety when flyinghigh in the atmosphere?

Topic: Fluids and PressureSciLinks code: HSM0586

Figure 6 Tornadoes are like giant vacuumcleaners because of pressure differences.

Answers to Section Review

1. Sample answer: A fluid is agas or a liquid. Atmosphericpressure is the pressurecaused by the weight of thegases in the atmosphere.

2. Sample answer: A pascalis a unit of pressure.

3. b4. Particles in the fluid collide

with the side of the container.The force of the collisions cre-ates pressure on the container.

5. You aren’t crushed byatmospheric pressure becausethe fluids inside your body exertpressure that works againstatmospheric pressure.

6. Atmospheric pressureincreases as depth increasesbecause at lower levels of theatmosphere, there is more airabove that is being pulled downby gravitational force.

7. Sample answer: Examplesof fluids flowing from highpressure to low pressure aredrinking through a straw,breathing, and squeezingtoothpaste from a tube.

8. pressure � 2.4 N �0.012 m2 � 200 Pa

9. Mercury has a higher den-sity than water. So, a givenvolume of mercury will weighmore than the same volume ofwater. Because pressuredepends on force (weight) andarea, mercury will exert morepressure than water will on thebottoms of identical containers.

10. As an airplane travels higher inthe atmosphere, the atmos-pheric pressure becomesmuch lower than it is on theground. At lower pressures,gas particles, including oxygenparticles, are farther apart.As a result, people have adifficulty breathing at lowpressures. Airplanes are pres-surized so that there is enoughoxygen for people to breathecomfortably.

CHAPTER RESOURCES


• Section Quizg• Section Reviewg• Vocabulary and Section Summaryg• Datasheet for Quick Lab

Technology

Transparencies• P24 Exhaling, Pressure, and Fluid Flow

CRF


READING STRATEGY

Buoyant ForceWhy does an ice cube fl oat on water? Why doesn’t it sink tothe bottom of your glass?

Imagine that you use a straw to push an ice cube under water.Then, you release the cube. A force pushes the ice back tothe water’s surface. The force, called buoyant forcebuoyant force (BOY uhntFAWRS), is the upward force that fluids exert on all matter.

Buoyant Force and Fluid PressureLook at Figure 1. Water exerts fluid pressure on all sides of anobject. The pressure exerted horizontally on one side of theobject is equal to the pressure exerted on the opposite side.These equal pressures cancel one another. So, the only fluidpressures affecting the net force on the object are at the topand at the bottom. Pressure increases as depth increases. So,the pressure at the bottom of the object is greater than thepressure at the top. The water exerts a net upward force onthe object. This upward force is buoyant force.

Determining Buoyant ForceArchimedes (AHR kuh MEE DEEZ), a Greek mathematician wholived in the third century BCE, discovered how to determinebuoyant force. Archimedes’ principleArchimedes’ principle states that the buoyantforce on an object in a fluid is an upward force equal tothe weight of the fluid that the object takes the place of, ordisplaces. Suppose the object in Figure 1 displaces 250 mL ofwater. The weight of that volume of displaced water is about2.5 N. So, the buoyant force on the object is 2.5 N. Notice thatonly the weight of the displaced fluid determines the buoyantforce on an object. The weight of the object does not affectbuoyant force.

Figure 1 There is more pressureat the bottom of an object becausepressure increases with depth. Thisresults in an upward buoyant forceon the object.

buoyant forcebuoyant force the upward forcethat keeps an object immersed in orfloating on a liquid

Archimedes’ principleArchimedes’ principle the princi-ple that states that the buoyant forceon an object in a fluid is an upwardforce equal to the weight of the vol-ume of fluid that the object displaces


Explain the relationship betweenfluid pressure and buoyant force.Predict whether an object will floator sink in a fluid.Analyze the role of density in anobject’s ability to float.Explain how the overall density ofan object can be changed.

Vocabularybuoyant forceArchimedes’ principle

Discussion Read this section silently.Write down questions that you haveabout this section. Discuss yourquestions in a small group.

2

OverviewThis section describes how dif-ferences in fluid pressure createbuoyant force. Students areintroduced to Archimedes’ prin-ciple and learn how to find thebuoyant force on an object.Finally, students learn the fac-tors that determine whether anobject floats or sinks in a fluid.

BellringerAsk your students to identifywhich of the following objectswill float in water: a rock, anorange, a screw, a quarter, a can-dle, a plastic-foam “peanut,”and a chalkboard eraser. Ask stu-dents to write a hypothesisabout why an aircraft carrier,which weighs thousands of tons,does not sink.

Demonstration --------------gDensity Layers Layer 20 mLeach of corn syrup, water, andcooking oil in a 100 mL gradu-ated cylinder. Have studentsobserve as you drop in objectsthat will float on the differentlayers. You might also try addingdroplets of alcohol. Use theresults of the demonstration tolaunch a discussion aboutbuoyant force. l Visual

CHAPTER RESOURCES


CRF • Lesson Plan• Directed Reading Ab• Directed Reading Bs

Technology

Transparencies• Bellringer

Workbooks


Q: Why did the banker jump into the

swimming pool?

A: He needed to float a loan.


Weight Versus Buoyant ForceAn object in a fluid will sink if its weight is greater than thebuoyant force (the weight of the fluid it displaces). An objectfloats only when the buoyant force on the object is equal tothe object’s weight.

SinkingThe rock in Figure 2 weighs 75 N. It displaces 5 L of water.Archimedes’ principle says that the buoyant force is equal to theweight of the displaced water—about 50 N. The rock’s weightis greater than the buoyant force. So, the rock sinks.

FloatingThe fish in Figure 2 weighs 12 N. It displaces a volume of waterthat weighs 12 N. Because the fish’s weight is equal to thebuoyant force, the fish floats in the water. In fact, the fish issuspended in the water as it floats. Now, look at the duck. Theduck does not sink. So, the buoyant force on the duck mustbe equal to the duck’s weight. But the duck isn’t all the wayunderwater! Only the duck’s feet, legs, and stomach have to beunderwater to displace 9 N of water, which is equal to the duck’sweight. So, the duck floats on the surface of the water.

Buoying UpIf the duck dove underwater, it would displace more than 9 Nof water. So, the buoyant force on the duck would be greaterthan the duck’s weight. When the buoyant force on an objectis greater than the object’s weight, the object is buoyed up(pushed up) in water. An object is buoyed up until the partof the object underwater displaces an amount of water thatequals the object’s entire weight. Thus, an ice cube pops to thesurface when it is pushed to the bottom of a glass of water.

✓✓Reading Check What causes an object to buoy up? (See theAppendix for answers to Reading Checks.)

Weight � 9 NBuoyant force � 9 NDuck floats on the surface.

Weight � 75 NBuoyant force � 50 NRock sinks.

Weight � 12 NBuoyant force � 12 NFish floats and issuspended in the water.

Figure 2 Will an object sink orfloat? That depends on whetherthe buoyant force is less than orequal to the object’s weight.

Floating FunFill a sink with water. Ask anadult to help you find fivethings that float in water andfive things that sink in water.Discuss what the floatingobjects have in common andwhat the sinking objects havein common. In your sciencejournal, list the objects, andsummarize your discussion.

READINGSTRATEGY ------------------g

Prediction Guide Before stu-dents read the next three pages,ask them to predict whether thefollowing statements are true orfalse:

1. The shape of an object helpsdetermine whether the objectwill float. (true)

2. Something made of steel can-not float in water. (false)

3. Whether an object floatsdepends on its weight. (true)

Have students evaluate theiranswers after they read the nextthree pages. l Logical

CONNECTIONCONNECTION vvMath ----------------------------------------------------------------------------a

Determining Weight Ask stu-dents to solve the followingproblem: “A force of 15 N isrequired to lift an object that isunderwater. The object displaces2 L of water (1 L of water weighs10 N). What is the weight of theobject out of water?” (forcerequired to lift object in water �

weight of object out of water �

buoyant force

15 N � weight of object out ofwater � 20 N

weight of object out of water �

20 N � 15 N � 35 N) l Logical

h-----------------------------g

Concept Mapping Have students create abuoyant force concept map and discussobjects that float on the surface of water,objects that float between the surface andthe bottom, and objects that sink to thebottom. l Verbal


An object is buoyed up if the buoyant force onthe object is greater than the object’s weight.

Section 2 • Buoyant Force 187

Floating, Sinking, and DensityThink again about the rock in the lake. The rock displaces 5 L of water. But volumes of solids are measured in cubic centimeters (cm3). Because 1 mL is equal to 1 cm3, the volume of the rock is 5,000 cm3.But 5,000 cm3 of rock weighs more than an equal volume of water. So, the rock sinks.

Because mass is proportional to weight, you can say that the rock has more mass per volume than water has. Mass per unit volume is density. The rock sinks because it is more dense than water is. The duck floats because it is less dense than water is. The density of the fish is equal to the density of the water.

More Dense Than AirWhy does an ice cube float on water but not in air? An ice cube floats on water because it is less dense than water. But most substances are more dense than air. So, there are few substances that float in air. The ice cube is more dense than air, so the ice cube doesn’t float in air.

Less Dense Than AirOne substance that is less dense than air is helium, a gas. In fact, helium has one-seventh the density of air under normal conditions. A given volume of helium displaces an equal volume of air that is much heavier than itself. So, helium floats in air. Because helium floats in air, it is used in parade balloons, such as the one shown in Figure 3.

✓Reading Check Name a substance that is less dense than air.

Figure 3 Helium in a balloon floats in air for the same reason an ice cube floats on water—helium is less dense than the surrounding fluid.

Finding Density Find the density of a rock that has a mass of 10 g and a volume of 2 cm3.

Step 1: Write the equation for density. Density is calculated by using this equation:

Step 2: Replace mass and volume with the values in the problem, and solve.

Now It’s Your Turn1. What is the density of a 20 cm3 object

that has a mass of 25 g?2. A 546 g fish displaces 420 mL of water.

What is the density of the fish? (Note: 1 mL � 1 cm3)

3. A beaker holds 50 mL of a slimy green liquid. The mass of the liquid is 163 g. What is the density of the liquid?

density � volumemass

density � � 5 g/cm310 g2 cm3

vv--------------------------------------g

Making Models Have students make a model of a hot-air balloon. Before they begin, discuss how heating the air inside the balloon changes the balloon’s overall density and therefore changes its buoyancy. Provide students with tissue paper, tape, glue, string, and other materials to make a model balloon. Fill the completed models with hot air from a hair dryer. Release the model to see if it floats. Have students evaluate their balloon’s performance. l Kinesthetic

CONNECTIONCONNECTION vvMath -----------------------------------------------------------a

Rearranging the Density Equation Have students rearrange the equation for density to solve for mass and volume. (mass � density �

volume; volume � mass � density)Then, have students solve the following problems:

1. The density of the liquid mer-cury is 13.5 g/mL. What is the mass of a 2.4 mL sample of mercury? (32.4 g)

2. The density of aluminum is 2.7 g/cm3. What is the volume of a 9.45 g sample of aluminum? (3.5 cm3)

l Logical


Helium is less dense than air.

Answers to Math Focus

1. 1.25 g/cm3

2. 1.3 g/cm3

3. 3.26 g/mL

Is That a Fact!Before plastics can be recycled, they must first be separated by type. Most containers display a number that identi-fies the type of plastic used. Containers that do not display number codes can be separated by density by being floated in liquids of different densities.


Floating Rocks The rock thatmakes up Earth’s continents isabout 15% less dense than themolten (melted) mantle rockbelow it. Because of this differ-ence in density, the continentsare floating on the mantle.Research the structure of Earth,and make a poster that showsEarth’s interior layers.

Changing Overall DensitySteel is almost 8 times denser than water. And yet huge steelships cruise the oceans with ease. But hold on! You just learnedthat substances that are more dense than water will sink inwater. So, how does a steel ship float?

Changing ShapeThe secret of how a ship floats is in the shape of the ship.What if a ship were just a big block of steel, as shown inFigure 4? If you put that block into water, the block would sinkbecause it is more dense than water. So, ships are built with ahollow shape. The amount of steel in the ship is the same asin the block. But the hollow shape increases the volume of theship. Remember that density is mass per unit volume. So, anincrease in the ship’s volume leads to a decrease in its density.Thus, ships made of steel float because their overall density isless than the density of water.

Most ships are built to displace more water than is neces-sary for the ship to float. Ships are made this way so that theywon’t sink when people and cargo are loaded on the ship.

A block of steelis more densethan water, so itsinks.

Shaping the steelinto a hollow formincreases the volumeoccupied by the samemass. The overalldensity of the ship isreduced. The ship isless dense than water,so the ship fl oats.

Shape and Overall DensityFigure 4

For another activity relatedto this chapter, go togo.hrw.com and type in thekeyword HP5FLUW.

GroupGroup vv -------g

Buoyancy and Scuba DivingInvite a scuba diver to talk tothe class about diving, and askthe diver to explain some of theprinciples of buoyant force.Have the diver bring a regulatorand an air tank to demonstratetheir use. Encourage students toask questions. l Interpersonal

CONNECTION toCONNECTION toLife Science -----------------------------------g

Buoyant Force and Sea Organisms Havestudents investigate the physical adapta-tions that enable sea organisms to utilizebuoyant force. Have students select anorganism that interests them and write areport or create a poster or other presenta-tion describing the organism. l Verbal

CHAPTER RESOURCESTechnology

Transparencies• P25 Shape and Overall Density

Using the Figure -----g

Shape and Overall DensitySome students may have diffi-culty understanding how chang-ing the shape of a steel blockchanges the overall density.Place the teaching transparencyof Figure 4, “Shape and OverallDensity,” on the overhead pro-jector. Draw a line that connectsthe top edges of the two sides ofthe U-shaped steel. Explain tostudents that the volume of theship includes the steel sides ofthe ship and the air inside theship. Further explain thatbecause air is much less densethan water, the overall densityof the steel and the air is lessthan the density of water. So,the ship floats. l Visual

SUPPORT FOR

English LanguageLearnersSinking and FloatingA demonstration may helpstudents understand theconcept of density’s effecton how an object sinks orfloats. Fill a tall, transparentglass or jar about one-thirdfull with water, and mark thewater level. Add a golf ball tothe glass, and ask students todescribe what happens. (Theball sinks.) Mark the waterlevel again. Next, add salt tothe water until the golf ballfloats. Call on students to ex-plain these two occurrences interms of density. Direct theirattention to the explanationsin the textbook if necessary.l Verbal/Visual


Changing MassA submarine is a special kind of ship that can travel both on the surface of the water and underwater. Submarines have ballast tanks that can be opened to allow sea water to flow in. As water is added, the submarine’s mass increases, but its vol-ume stays the same. The submarine’s overall density increases so that it can dive under the surface. Crew members control the amount of water taken in. In this way, they control how dense the submarine is and how deep it dives. Compressed air is used to blow the water out of the tanks so that the submarine can rise. Study Figure 5 to learn how ballast tanks work.

✓Reading Check How do crew members control the density of a submarine?

When a submarine is floating on the ocean’s surface, its ballast tanks are filled mostly with air.

Ship Shape1. Roll a piece of clay into a ball the size of a golf ball, and drop

it into a container of water. Record your observations.2. With your hands, flatten the ball of clay until it is a bit thinner

than your little finger, and press it into the shape of a bowl or canoe.

3. Place the clay boat gently in the water. How does the change of shape affect the buoyant force on the clay? How is that change related to the overall density of the clay boat? Record your answers.

Controlling Density Using Ballast TanksFigure 5

Vent holes on the ballast tanks are opened to allow the subma-rine to dive. Air escapes as the tanks fill with water.

Vent holes are closed, and com-pressed air is pumped into the ballast tanks to force the water out, so the submarine rises.

Air

Ballast tanks

Reteaching -------------------------------------bRubber Ducky Place a rubber duck in a large, clear container of water. Explain to students that the overall density of the rubber and the air allows the duck to float. Then, cut the duck in two and put the pieces in the water. Explain that the pieces sink because there is no air trapped inside the duck and the rubber is more dense than water. l Visual

Quiz --------------------------------------------------------------------g

1. How can you determine the buoyant force acting on an object? (Determine the weight of the volume of fluid displaced by the object.)

2. Who discovered how to deter-mine buoyant force?(Archimedes)

3. How can a scuba diver keep from floating back to the sur-face of the water? (The diver can add weights.)


Crew members control the density of a submarine by controlling the amount of water in the ballast tanks.

M A T E R I A L SFOR EACH STUDENT

• bowl or pail, medium, one for every two or three students

• clay, modeling, golf-ball-sized piece• water

Answer

3. Forming the clay into a boat shape causes the clay to displace more water, which increases the buoyant force. The change in shape causes the overall density of the clay boat to decrease so that the clay boat is less dense than the water. Therefore, the clay boat floats.


For a variety of links related to thischapter, go to www.scilinks.org

SummarySummary

Review

Changing VolumeLike a submarine, some fish adjust their over-all density to stay at a certain depth in thewater. Most bony fishes have an organ called aswim bladder, shown in Figure 6. This swim blad-der is filled with gases produced in a fish’s blood.The inflated swim bladder increases the fish’svolume and thereby decreases the fish’s overalldensity, which keeps the fish from sinking inthe water. The fish’s nervous system controls theamount of gas in the bladder. Some fish, such assharks, do not have a swim bladder. These fishmust swim constantly to keep from sinking.

• All fluids exert anupward force calledbuoyant force.

• Buoyant force is causedby differences in fluidpressure.

• Archimedes’ principlestates that the buoyantforce on an object isequal to the weight ofthe fluid displaced bythe object.

• Any object that is moredense than the sur-rounding fluid will sink.An object that is lessdense than the sur-rounding fluid will float.

• The overall density of anobject can be changedby changing the object’sshape, mass, or volume.

Using Key Terms

1. Use the following terms in thesame sentence: buoyant force andArchimedes’ principle.


2. Which of the following changesincreases the overall density ofthe object?

a. A block of iron is formed intoa hollow shape.

b. A submarine fills its ballasttanks with water.

c. A submarine fills its ballasttanks with air.

d. A fish increases the amountof gas in its swim bladder.

3. Explain how differences in fluidpressure create buoyant force onan object.

4. How does an object’s densitydetermine whether the objectwill sink or float in water?

5. Name three methods that canbe used to change the overalldensity of an object.

Math Skills

6. What is the density of an objectthat has a mass of 184 g and avolume of 50 cm3?

Critical Thinking

7. Applying Concepts An objectweighs 20 N. It displaces a vol-ume of water that weighs 15 N.

a. What is the buoyant force onthe object?

b. Will this object float or sink?Explain your answer.

8. Predicting Consequences Ironhas a density of 7.9 g/cm3.Mercury is a liquid that has adensity of 13.5 g/cm3. Will ironfloat or sink in mercury? Explainyour answer.

9. Evaluating Hypotheses Imag-ine that your brother tells youthat all heavy objects sink inwater. Explain why you agreeor disagree with his statement.

Topic: Buoyant ForceSciLinks code: HSM0202

Figure 6 Most bony fishes have anorgan called a swim bladder that allowsthem to adjust their overall density.

Swim bladder

AlternativeAssessment ---------------------------g

Life Jackets Ask students tomake a poster that explains howa life jacket helps a person float.(Most life jackets are made fromporous material filled with air.)(A life jacket keeps a person fromsinking because the air inside thelife jacket increases the person’svolume but does not increase his orher weight by very much. The per-son’s overall density decreases, andthe person floats.) l Visual


1. Sample answer: Archimedes’principle is about the relation-ship between the buoyant forceof an object and the amount ofwater the object displaces.

2. b3. Water pressure is exerted on all

sides of an object. The pressuresexerted horizontally on the sidescancel each other out. The pres-sure exerted at the bottom isgreater than that exerted at thetop because pressure increaseswith depth. This creates an over-all upward force on the object—the buoyant force.

4. An object will float in water if itsdensity is less than the density ofwater. An object will sink inwater if its density is greaterthan the density of water.

5. The density of an object can bechanged by changing the shape,mass, or volume of an object.

6. 184 g � 50 cm3 � 3.68 g/cm3

7. a. 15 Nb. It will sink because its weight

is greater than the buoyantforce acting on it.

8. Iron will float in mercurybecause iron is less dense thanmercury.

9. Sample answer: I disagree withthis statement because steelships are heavy but they float inwater. The ships float becausethe overall density of the steeland the air inside the ship is lessthan the density of water.

CHAPTER RESOURCES


• Section Quizg• Section Reviewg• Vocabulary and Section Summaryg• SciLinks Activityg• Datasheet for Quick Lab

Technology

Transparencies• P26 Controlling Density Using Ballast Tanks

Interactive Explorations CD-ROM• Sea the Lightg

CRF


READING STRATEGY

Fluids and MotionHold two sheets of paper so that the edges are hanging in front of your face about 4 cm apart. The fl at faces of the paper should be parallel to each other. Now, blow as hard as you can between the two sheets of paper.

What’s going on? You can’t separate the sheets by blowingbetween them. In fact, the sheets move closer together theharder you blow. You may be surprised that the explanationfor this unusual occurrence also includes how wings help birdsand planes fly and how pitchers throw screwballs.

Fluid Speed and PressureThe strange reaction of the paper is caused by a property ofmoving fluids. This property was first described in the 18thcentury by Daniel Bernoulli (ber NOO lee), a Swiss mathemati-cian. Bernoulli’s principleBernoulli’s principle states that as the speed of a movingfluid increases, the fluid’s pressure decreases. In the case ofthe paper, air speed between the two sheets increased whenyou blew air between them. Because air speed increased, thepressure between the sheets decreased. Thus, the higherpressure on the outside of the sheets pushed them together.

Science in a SinkBernoulli’s principle is at work in Figure 1. A table-tennis ball isattached to a string and swung into a stream of water. Insteadof being pushed out of the water, the ball is held in the water.Why? The water is moving faster than the air around it, sothe water has a lower pressure than the surrounding air. Thehigher air pressure pushes the ball into the area of lower pres-sure—the water stream. Try this at home to see for yourself!

Figure 1 This ball is pushed by the higher pressure of the air into an area of reduced pressure—the water stream.

Bernoulli’s principleBernoulli’s principle the principle that states that the pressure in a fluid decreases as the fluid’s velocity increases


Describe the relationship betweenpressure and fluid speed.Analyze the roles of lift, thrust, andwing size in flight.Describe drag, and explain how itaffects lift.Explain Pascal’s principle.

VocabularyBernoulli’s principleliftthrustdragPascal’s principle

Reading Organizer As you read thissection, create an outline of the sec-tion. Use the headings from the sec-tion in your outline.

3

OverviewIn this section, students learnabout Bernoulli’s principle. Theythen explore how objects thatare heavier than air can achieveflight. Students also learn aboutthe basic aspects of flight.Finally, students learn aboutPascal’s principle.

BellringerPose the following problem toyour students: “You have beenasked to design two kites. Onekite will be flown in areas wherethere is almost always a goodbreeze. The other kite will beflown in areas with very littlewind.” What differences indesign and materials are therebetween your two kites?

Demonstration --------------gMagic Water Place a strawupright in a glass of water. Holda second straw at a right angle atthe top of the first so that thestraws are just touching. Blowvery hard through the horizon-tal straw. Water will rise up inthe vertical straw and form aspray. Tell students they willlearn why this occurs after read-ing this section. l Visual

CHAPTER RESOURCES


CRF • Lesson Plan• Directed Reading Ab• Directed Reading Bs

Technology

Transparencies• Bellringer• P27 Wing Design and Lift

Workbooks



Factors That Affect FlightA common commercial airplane in the skies today is the Boeing 737 jet. Even without passengers, the plane weighs 350,000 N. How can something so big and heavy get off the ground and fly? Wing shape plays a role in helping these big planes—as well as smaller planes and birds—achieve flight, as shown in Figure 2.

According to Bernoulli’s principle, the fast-moving air above the wing exerts less pressure than the slow-moving air below the wing. The greater pressure below the wing exerts an upward force. This upward force, known as lift, pushes the wings (and the rest of the airplane or bird) upward against the downward pull of gravity.

✓Reading Check What is lift? (See the Appendix for answers to Reading Checks.)

bAirplane wings are made so that the air speed above the wing is greater than the air speed below the wing.

According to Bernoulli’s principle, a difference in air speed means a difference in pressure. The result is an upward force that contrib-utes to lift.

Another feature of wing design is that the shape of the wing forces the air downward. So, the air pushes the wing upward.

a

c

lift an upward force on an object that moves in a fluid

Figure 2 Wing Design and Lift

vv--------------------------------------------------------b

Pressure Analogy Before you discuss Bernoulli’s principle, it may help some students to imagine the pressure of a fluid as the combined pressure of many particles striking a surface. Have students imagine a swarm of bees trapped in a short sec-tion of a long piece of pipe. As the bees fly around inside the pipe, they bounce off each other and off the walls of the pipe, creating pressure. Then, have students imagine that the bees are suddenly able to fly the entire length of the pipe. Explain that, because the bees have more room, they bounce against the walls of the pipe much less frequently, creating less pressure inside the pipe. l Verbal/Logical

vv--------------------------------------a

Wing Shape Ask students to examine the wing shape shown in Figure 2. Have students use their knowledge of Bernoulli’s principle to hypothesize about what type of wings might work in flight. Does the wing have to be curved? Is flight possible without wings? l Logical/Visual

Demonstration --------------g

Flying Ball Point the airflow of a portable hair dryer straight up, and suspend a table-tennis ball in the airstream. Change the direction of the airflow slightly to maneuver the ball. Have stu-dents speculate on the forces that are at work in this demonstration. l Visual


Lift is an upward force on an object that is moving in a fluid.

MISCONCEPTIONALERT

More Than Bernoulli When teaching about airplane flight, emphasize that there is more to understanding lift than can be explained by Bernoulli’s princi-ple. Newton’s third law also plays a part. A tilted wing deflects horizontal airflow downward (the action force exerted by the wing on the air). The reaction force is the upward force the air exerts on the wing. This force also contributes to lift.

Section 3 • Fluids and Motion 193

Thrust and LiftThe amount of lift created by a plane’s wing is determinedpartly by the speed at which air travels around the wing. Thespeed of a plane is determined mostly by its thrust. Thrust isthe forward force produced by the plane’s engine. In general, aplane with a large amount of thrust moves faster than a planethat has less thrust does. This faster speed means air travelsaround the wing at a higher speed, which increases lift.

Wing Size, Speed, and LiftThe amount of lift also depends partly on the size of a plane’swings. Look at the jet plane in Figure 3. This plane can flywith a relatively small wing size because its engine gives a largeamount of thrust. This thrust pushes the plane through the skyat great speeds. So, the jet creates a large amount of lift withsmall wings by moving quickly through the air. Smaller wingskeep a plane’s weight low, which also helps it move faster.

Compared with the jet, the glider in Figure 3 has a largewing area. A glider is an engineless plane. It rides rising aircurrents to stay in flight. Without engines, gliders produceno thrust and move more slowly than many other kinds ofplanes. Thus, a glider must have large wings to create the liftit needs to stay in the air.

Bernoulli and BirdsBirds don’t have engines, so birds must flap their wings to pushthemselves through the air. A small bird must flap its wings ata fast pace to stay in the air. But a hawk flaps its wings onlyoccasionally because it has larger wings than the small birdhas. A hawk uses its large wings to fly with very little effort.Fully extended, a hawk’s wings allow the hawk to glide onwind currents and still have enough lift to stay in the air.

Increased Thrust Versus Increased Wing SizeFigure 3

thrust the pushing or pulling forceexerted by the engine of an aircraftor rocket

The First Flight The firstsuccessful flight of an engine-driven machine that washeavier than air happened inKitty Hawk, North Carolina, in1903. Orville Wright was thepilot. The plane flew only 37 m(about the length of a 737jet) before landing, and theentire flight lasted only 12 s.Research another famous pilotin the history of flight. Make aposter that includes informa-tion about the pilot as well aspictures of the pilot and his orher airplane.

The engine of this jet creates alarge amount of thrust, so thewings don’t have to be very big.

This glider has no engine andtherefore no thrust. So, its wingsmust be large in order to maxi-mize the amount of lift achieved.

StrategiesStrategiesINCLUSIONINCLUSION

• Hearing Impaired• Learning Disabled• Developmentally DelayedThe concept of airplane liftis complicated for studentswith language delays tounderstand. Use this experi-ment to give them a chanceto experience the idea of lift.Organize the students intosmall groups. Give eachgroup an 8 1/2 in. � 11 in.sheet of paper and an11 in. � 17 in. sheet of paper.Ask each team to make twopaper airplanes that are alikeexcept that one has muchlarger wings. Ask students tonote the lift of each plane asthey do the following: Throwthe two planes with the sameforce. Throw the short-wingedplane with light force andthen with heavy force. Throwthe long-winged plane withlight force and then withheavy force.l Kinesthetic ee

vv--------------------------------------a

Wind Tunnels Have studentsresearch how engineers usewind tunnels to test the designof airplane wings. Then, havestudents use what they havelearned to build their own wingsand wind tunnel, and show theclass how to test the wing designs.l Kinesthetic CHAPTER RESOURCES

Technology

Transparencies• P28 Bernoulli’s Principle and the Screwball

CulturalAwarenessCulturalAwareness g

Boomerangs More than 8,000 yearsago, Australian aborigines discoveredthe aerodynamic qualities of a type ofhunting stick called a boomerang. Havestudents research boomerangs and com-pare a boomerang’s flight with an air-plane’s flight. Ask students to presenttheir findings in a poster. l Visual


Bernoulli and BaseballYou don’t have to look up at a bird or a plane flying throughthe sky to see Bernoulli’s principle in your world. Any timefluids are moving, Bernoulli’s principle is at work. Figure 4shows how a baseball pitcher can take advantage of Bernoulli’sprinciple to throw a confusing screwball that is difficult fora batter to hit.

Drag and Motion in FluidsHave you ever walked into a strong wind and noticed that thewind seemed to slow you down? It may have felt like the windwas pushing you backward. Fluids exert a force that opposesthe motion of objects moving through the fluids. The forcethat opposes or restricts motion in a fluid is called drag.drag.

In a strong wind, air “drags” on your body and makes itdifficult for you to move forward. Drag also works against theforward motion of a plane or bird in flight. Drag is usuallycaused by an irregular flow of air. An irregular or unpredict-able flow of fluids is known as turbulence.

✓✓Reading Check What is turbulence?

Bernoulli’s Principle and the ScrewballFigure 4

Directionof airflow

Directionof spin

Because air pressure on the left side is greater than air pressure on the right side, the ball is pushed toward the right in a curved path.

c

a Air speed on the left side of the ball is decreased because air around the ball moves in the opposite direction of the airfl ow. So, there is a region of increased pressure on the left side of the ball.

dragdrag a force parallel to the velocity of the flow; it opposes the direction of an aircraft and, in combination with thrust, determines the speed of the aircraft

Air speed on the right side of the ball is increased because air around the ball moves in the same direction as the airfl ow. So, there is a region of decreased pressure on the right side of the ball.

b

CONNECTIONCONNECTION vvLanguage Arts -------------------------g

Writing Bird Story Have stu-dents imagine that theyare a hawk or an alba-

tross. Have students write a one-page story describing how theprinciples of flight apply to themas they travel through the sky.Students may need to researchthe bird of their choice beforewriting their stories. l Verbal

GroupGroup vv -------g

Safety Caution: Caution stu-dents to wear goggles, gloves,and aprons while doing thisactivity.

Floating Bubbles Prepare asolution consisting of 250 mL ofdishwashing liquid, 50–60 dropsof glycerin, and 4.5 L of water.Give small groups of studentscontainers of the solution andstraws or other bubble-blowingtools. You may also want to pro-vide students with index cardsto help create a breeze. Ask thegroups to devise ways to keepthe bubbles from hitting thefloor. Have groups describemethods that increase thepressure below the bubblesor decrease the pressureabove them. l Kinesthetic


An irregular or unpredictable flowof fluids is known as turbulence.

h-----------------------------g

Pascal’s Principle andHydraulics Have studentsresearch hydraulic lifts that areused in auto repair shops. Askstudents to explain what thelifts have in common withpower brakes in automobiles.Ask students to make a diagramthat illustrates how a hydrauliclift system works. l Visual

SUPPORT FOR

English Language LearnersSpecialized Vocabulary As students readthrough this section they will encounternew specialized scientifi c meanings forwords they may have learned before.Ask them to keep a running list of wordsthey do not understand. When they havefi nished reading the section, ask them toread it again with a partner, using contextand the partner’s knowledge to help themdefi ne the new terms in their lists in theirown words. After the partner reading, if

there are still some terms left undefi ned,allow students to fi ll in the defi nitionsusing a dictionary. In addition, have themlook up the terms they defi ned throughcontext to verify their defi nitions. Thewords may include: reaction, property, lift,force, thrust, and drag. Check students’defi nitions for accuracy and languageusage. Have students make corrections ifnecessary.l Visual/Verbal/Interpersonal


Turbulence and LiftLift is often reduced when turbulence causes drag. Drag canbe a serious problem for airplanes moving at high speeds. So,airplanes are equipped with ways to reduce turbulence as muchas possible when in flight. For example, flaps like those shownin Figure 5 can be used to change the shape or area of a wing.This change can reduce drag and increase lift. Similarly, birdscan adjust their wing feathers in response to turbulence.

✓✓Reading Check How do airplanes reduce turbulence?

Pascal’s PrincipleImagine that the water-pumping station in your town increasesthe water pressure by 20 Pa. Will the water pressure be increasedmore at a store two blocks away or at a home 2 km away?

Believe it or not, the increase in water pressure will be thesame at both locations. This equal change in water pressure isexplained by Pascal’s principle. Pascal’s principlePascal’s principle states that achange in pressure at any point in an enclosed fluid will betransmitted equally to all parts of that fluid. This principle wasdiscovered by the 17th-century French scientist Blaise Pascal.

Pascal’s Principle and MotionHydraulic (hie DRAW lik) devices use Pascal’s principle to moveor lift objects. Liquids are used in hydraulic devices becauseliquids cannot be easily compressed, or squeezed, into a smallerspace. Cranes, forklifts, and bulldozers have hydraulic devicesthat help them lift heavy objects.

Hydraulic devices can multiply forces. Car brakes are agood example. In Figure 6, a driver’s foot exerts pressure on acylinder of liquid. This pressure is transmitted to all parts of theliquid-filled brake system. The liquid moves the brake pads. Thepads press against the wheels, and friction stops the car. Theforce is multiplied because the pistons that push the brake padsare larger than the piston that is pushed by the brake pedal.

Figure 5 The pilot of this airplane can move these flaps to adjust the amount of lift when the airplane lands or takes off.

Pascal’s principlePascal’s principle the principle that states that a fluid in equilibrium contained in a vessel exerts a pressure of equal intensity in all directions


Airplanes can reduce turbulence by changingthe shape or area of the wings.

Reteaching -------------------------------------bSeeing Turbulence Give pairsof students a shallow pan ofwater and an index card. Tellstudents to slowly drag theindex card through the waterand to watch the water behindthe card. Tell students that theripples behind the card and theswirls that come off the edge ofthe card are examples ofturbulence. l Visual

Quiz --------------------------------------------------------------------g

1. What forces act on anaircraft? (lift, thrust, drag,and gravity)

2. When an airplane is flying,how does the air pressureabove a wing compare withthat below the wing? (Air pres-sure above the wing is lower.)

3. How is thrust related to thespeed of an airplane? (Thespeed of an airplane increases asits thrust increases.)

AlternativeAssessment ---------------------------g

Aircraft Chart Display two orthree photographs or models ofdifferent types of aircraft, suchas a glider, a jet, a biplane, oreven an airship. Ask students toselect two of the aircraft and tomake a chart that compares andcontrasts the aircraft in terms oflift, drag, thrust, and gravity.l Verbal


For a variety of links related to this chapter, go to www.scilinks.org

SummarySummary

Review

• Bernoulli’s principle states that fluid pressure decreases as the speed of the fluid increases.

• Wing shape allows air-planes to take advantage of Bernoulli’s principle to achieve flight.

• Lift on an airplane is determined by wing size and thrust.

• Drag opposes motion through fluids.

• Pascal’s principle states that a change in pres-sure in an enclosed fluid is transmitted equally to all parts of the fluid.

Using Key Terms

For each pair of terms, explain how the meanings of the terms differ.

1. Bernoulli’s principle and Pascal’s principle

2. thrust and drag


3. The shape of an airplane’s wing helps it gain

a. drag. c. thrust.b. lift. d. turbulence.

4. What is the relationship between pressure and fluid speed?

5. What is Pascal’s principle?

6. What force opposes motion through a fluid? How does this force affect lift?

7. How do thrust and lift help an airplane achieve flight?

Critical Thinking

8. Applying Concepts Air moving around a speeding race car can create lift. Upside-down wings, or spoilers, are mounted on the rear of race cars. Use Bernoulli’s principle to explain how spoilers reduce the danger of accidents.

9. Making Inferences When you squeeze a balloon, where is the pressure inside the balloon increased the most? Explain.

Interpreting Graphics

10. Look at the image below. When the space through which a fluid flows becomes narrow, fluid speed increases. Using this information, explain how the two boats could collide.

Topic: Bernoulli’s PrincipleSciLinks code: HSM0143

Figure 6 Because of Pascal’s principle, the touch of a foot can stop tons of moving metal.

When the driver pushes the brake pedal, a small piston exerts pressure on the fluid inside the brake system.

The change in pressure is trans-mitted to the large pistons that push on the brake pads.

1

2


1. Bernoulli’s principle states that the pressure in a fluid decreases as the fluid’s velocity increases. Pascal’s principle states that a fluid in an enclosed container exerts pressure equally in all directions.

2. Thrust is the pushing or pulling force exerted by the engine of an airplane that moves the airplane forward. Drag is a force that opposes motion in a fluid.

3. b4. As fluid speed increases,

the pressure exerted by the fluid decreases.

5. Pascal’s principle states that an enclosed fluid exerts pressure equally in all directions.

6. Drag is a force that opposes motion through a fluid. Lift is often reduced when turbulence causes drag.

7. Lift helps an airplane achieve flight by pushing the airplane up. Thrust helps an airplane achieve flight by causing the airplane to move faster through the air. The faster speed means that air travels faster around the wings, which increases lift.

8. Sample answer: Air traveling around the spoiler produces a downward force. This down-ward force pushes down on the rear of the car and helps keep the rear wheels of the cars in contact with the road. The cars travel more safely because the rear wheels stay in contact with the road.

9. The pressure inside the bal-loon increases equally in all directions. Squeezing a balloon demonstrates Pascal’s principle.

10. As the fluid speed between the boats increases, the fluid pres-sure decreases. The pressure on the outer sides of the boats then becomes greater than the pressure between them. This increased pressure from the outside can push the boats together, causing them to collide.

CHAPTER RESOURCES


• Section Quiz g• Section Review g• Vocabulary and Section Summary g• Reinforcement Worksheet b• Critical Thinking a

CRF


LabSkills Practice

Calculate the buoyant forceon an object.

Compare the buoyant forceon an object with its weight.

• balance

• mass set

• pan, rectangular baking

• paper towels

• ruler, metric

• tub, plastic, large rectangular

• water

Fluids, Force, and FloatingWhy do some objects sink in fluids but others float? In thislab, you’ll get a sinking feeling as you determine that an objectfloats when its weight equals the buoyant force exerted bythe surrounding fluid.

Procedure

1 Copy the table shown below.

2 Fill the tub half full with water. Measure (in centimeters)the length, width, and initial height of the water. Record yourmeasurements in the table.

3 Using the equation given in the table, determine the initialvolume of water in the tub. Record your results in the table.

4 Place the pan in the water, and place masses in the pan,as shown on the next page. Keep adding masses until thepan sinks to about three-quarters of its height. Record thenew height of the water in the table. Then, use this value todetermine and record the new total volume of water plus thevolume of water displaced by the pan.

Measurement Trial 1 Trial 2Length (l), cm

Width (w), cm

Initial height (h1), cm

Initial volume (V1), cm3

V1 � l � w � h1

New height (h2), cm

New total volume (V2), cm3

V2 � l � w � h2

Displaced volume (�V), cm3

�V � V2 � V1

Mass of displaced water, gm � �V � 1 g/cm3

Weight of displaced water, N(buoyant force)

Weight of pan and masses, N

OBJECTIVES

MATERIALS

SAFETY DO NOTDO NOTDO NOT

TE IN

WRITEITE I

BOOKO

Skills PracticeSkills Practice LabLab

Fluids, Force, andFloating

Teacher’s Notes

Time RequiredOne to two 45-minute classperiods

Lab Ratings

rTeacher Prep f

Student Set-Up ff

Concept Level fff

Clean Up f

M A T E R I A L SThe supplies listed are for one groupof 3– 4 students. The tank or tubshould have vertical sides. A smallor medium-sized tub works bestbecause changes in volume can beobserved easily. Masses should beadded near the center of the bakingpan. A fish tank or aquarium workswell for this activity.

Preparation NotesIf you use a tub or pan withoutvertical sides, the buoyant forceand the weight of the pan andmasses will not be equal. Inmost cases, the buoyant forcewill be greater than the weight.Have students measure the sideof the baking pan and mark theone-quarter, one-half, and three-quarter levels. Analyze theresults.

CHAPTER RESOURCES


CRF • Datasheet for Chapter Lab• Lab Notes and Answers

Technology

Classroom Videos• Lab Video

• Density Diver

Lab NotesVolumes of liquids are usually expressed inmilliliters (mL). Here, the volume measure-ments for the water displaced are basedon a rectangular container (the tank ortub), so cubic centimeters (cm3) are used.


5 Determine the volume of the water that wasdisplaced by the pan and masses, and recordthis value in the table. The displaced volume isequal to the new total volume minus the initialvolume.

6 Determine the mass of the displaced water bymultiplying the displaced volume by its density(1 g/cm3). Record the mass in the table.

7 Divide the mass by 100. The value you get isthe weight of the displaced water in newtons(N). This is equal to the buoyant force. Recordthe weight of the displaced water in the table.

8 Remove the pan and masses, and determinetheir total mass (in grams) using the balance.Convert the mass to weight (N), as you did instep 7. Record the weight of the masses andpan in the table.

9 Place the empty pan back in the tub. Performa second trial by repeating steps 4–8. Thistime, add masses until the pan is just aboutto sink.

Analyze the Results

1 Identifying Patterns Compare the buoyantforce (the weight of the displaced water) withthe weight of the pan and masses for bothtrials.

2 Examining Data How did the buoyant forcediffer between the two trials? Explain.

Draw Conclusions

3 Drawing Conclusions Based on your obser-vations, what would happen if you were to addeven more mass to the pan than you did in thesecond trial? Explain your answer in terms ofthe buoyant force.

4 Making Predictions What would happenif you put the masses in the water withoutthe pan? What difference does the pan’sshape make?

Analyze the Results

1. In each trial, the buoyant forceand the weight should be thesame.

2. The buoyant force is larger inthe second trial because morewater is displaced.

Draw Conclusions

3. The pan would sink becauseits weight would be greater butthe buoyant force (the weight ofthe water displaced) would beabout the same.

4. The masses would sink. Theshape of the pan allows themasses to displace more waterthan the masses alone displace.

CHAPTER RESOURCESWorkbooks

Whiz-Bang Demonstrations• The Rise and Fall of Raisinsg• Going Against the Flowg

EcoLabs & Field Activities• What’s the Flap All About?b

Long-Term Projects & Research Ideas• Scuba Divea

Sharon L. Woolf

Langston HughesMiddle SchoolReston, Virginia

Holt Lab Generator CD-ROMSearch for any lab by topic, standard, difficulty level,or time. Edit any lab to fit your needs, or create yourown labs. Use the Lab Materials QuickList softwareto customize your lab materials list.

CLASSROOM

TESTED& APPRO

VED

Chapter 7 • Chapter Lab 199

In each of the following sentences, replace the incorrect term with the correct term from the word bank.

thrust pressuredrag liftbuoyant force fluidPascal’s principleBernoulli’s principle

1 Lift increases with the depth of a fl uid.

2 A plane’s engines produce drag to push the plane forward.

3 A pascal can be a liquid or a gas.

4 A hydraulic device uses Archimedes’ principle to lift or move objects.

5 Atmospheric pressure is the upward force exerted on objects by fl uids.

Multiple Choice

6 The design of a wing

a. causes the air above the wing to travel faster than the air below the wing.

b. helps create lift.c. creates a low-pressure zone above

the wing.d. All of the above

7 Fluid pressure is always directed

a. up. c. sideways.b. down. d. in all directions.

8 An object surrounded by a fl uid will displace a volume of fl uid that is

a. equal to its own volume.b. less than its own volume.c. greater than its own volume.d. denser than itself.

9 If an object weighing 50 N displaces a volume of water that weighs 10 N, what is the buoyant force on the object?

a. 60 N c. 40 Nb. 50 N d. 10 N

0 A helium-fi lled balloon will fl oat in air because

a. there is more air than helium.b. helium is less dense than air.c. helium is as dense as air.d. helium is more dense than air.

q Materials that can fl ow to fi t their containers include

a. gases.b. liquids.c. both gases and liquids.d. gases, liquids, and solids.

USING KEY TERMS

UNDERSTANDING KEY IDEAS

ANSWERS

Using Key Terms1. replace lift with pressure2. replace drag with thrust3. replace pascal with fluid4. replace Archimedes’ prin-

ciple with Pascal’s principle5. replace Atmospheric pres-

sure with Buoyant force

Understanding Key Ideas6. d7. d8. a9. d

10. b11. c

Assignment GuideSECTION QUESTIONS

1 1, 3, 7, 11–15, 20–21

2 5, 8–10, 18, 22–24

3 2, 4, 6, 17, 19

1 and 2 16


Short Answer

w Where is water pressure greater, at adepth of 1 m in a large lake or at adepth of 2 m in a small pond? Explainyour answer.

e Why are bubbles round?

r Why are tornadoes like giant vacuumcleaners?

Math Skills

t Calculate the area of a 1,500 N objectthat exerts a pressure of 500 Pa(500 N/m2). Then, calculate thepressure exerted by the same objectover twice that area.

yConcept Mapping Use the followingterms to create a concept map: fl uid,pressure, depth, density, and buoyantforce.

uForming Hypotheses Gases can beeasily compressed into smaller spaces.Why would this property of gasesmake gases less useful than liquids inhydraulic brakes?

iMaking Comparisons Will a shiploaded with beach balls fl oat higheror lower in the water than an emptyship? Explain your reasoning.

oApplying Concepts Inside all vacuumcleaners is a high-speed fan. Explainhow this fan causes the vacuumcleaner to pick up dirt.

pEvaluating Hypotheses A 600 N girlon stilts says to two 600 N boyssitting on the ground, “I am exertingover twice as much pressure as thetwo of you are exerting together!”Could this statement be true? Explainyour reasoning.

Use the diagram of an iceberg below toanswer the questions that follow.

a At what point (a, b, or c) is waterpressure greatest on the iceberg?

s How much of the iceberg has a weightequal to the buoyant force?

a. all of itb. the section from a to bc. the section from b to cd. None of the above

d How does the density of ice comparewith the density of water?

f Why do you think icebergs aredangerous to passing ships?

a

b

c

CRITICAL THINKING

INTERPRETING GRAPHICS

12. Water pressure is greater at a depth of 2 min a small pond. Pressure increases withdepth regardless of the amount of fluidpresent.

13. Bubbles are round because air, like allfluids, exerts pressure evenly in all direc-tions. So, when you blow a bubble, the bub-ble expands in all directions to create asphere.

14. Tornadoes are like giant vacuum cleanersbecause the air rushing into the tornadopushes objects into a tornado. This processis similar to the way dirt is pushed into avacuum cleaner.

15. 3 m2; 250 Pa

Critical Thinking16. An answer to this

exercise can befound at the endof this book.

17. If a gas were used in hydraulicbrakes, the brakes would notwork. When the brake pedal ispushed, the gas would com-press and therefore would notpush on the brake pads to stopthe wheels.

18. The ship will float lower in thewater because the beach ballswill add to the total mass of theship but will not increase thevolume. Therefore, the overalldensity of the ship will increase,causing the ship to sink a little.

19. The fan causes the air insidethe vacuum cleaner to movefaster, which decreases pres-sure. The higher air pressureoutside of the vacuum thenpushes dirt into the vacuumcleaner.

20. Yes, the statement could betrue. Pressure is equal to forcedivided by area. The girl onstilts is exerting force over amuch smaller area than the twoboys on the ground are. There-fore, it is possible that the girlis exerting twice as much pres-sure as the two boys are.

Interpreting Graphics21. c22. a23. Ice is less dense than water.24. Only a small portion of an ice-

berg floats above water, asshown in the image. A ship mayactually be closer to runninginto a massive block of iceunderwater than it wouldappear on the surface. If theship is not turned or stopped intime, it could collide with theiceberg.

CHAPTER RESOURCES


CRF • Chapter Reviewg• Chapter Test Ag• Chapter Test Ba• Chapter Test Cs• Vocabulary Activityg

Workbooks

Study Guide• Study Guide is also available in Spanish.

Chapter 7 • Chapter Review 201

READING

MISCONCEPTIONALERT

Teacher’s NoteTeacher’s NoteTo provide practice under more realistic testing conditions, give students 20 minutes to answer all of the questions in this Standardized Test Preparation.

Answers to the standardized test preparation can help you identify student misconcep-tions and misunderstandings.

READINGRead each of the passages below. Then, answer the questions that follow each passage.

Passage 1 The Mariana Trench is about 11 km deep—that’s deep enough to swallow Mount Everest, the tallest mountain in the world. Fewer than a dozen undersea vessels have ever ventured this deep into the ocean. Why? Water exerts tremendous pressure at this depth. A revolutionarynew undersea vessel, Deep Flight, has a hull made of an extremely strong ceramic material that can withstand such pressure. Although Deep Flighthas not made it to the bottom of the Mariana Trench, some scientists think this type of undersea vessel will one day be used routinely to explore the ocean floor.

1. What is the meaning of the word revolutionary in this passage?

A strangeB overthrowing the governmentC radically differentD disgusting

2. Based on the name of the undersea vessel described in this passage, what does the vessel look like?

F a robotG a houseH a carI an airplane

3. Based on the passage, which of the following statements is a fact?

A Scientists hope to fl y Deep Flight to the top of Mount Everest.

B Deep Flight can withstand very high pressures.

C Scientists cannot explore the ocean without using Deep Flight.

D Deep Flight has gone to the bottom of the Mariana Trench a dozen times.

Passage 2 Buoyancy is an object’s ability to float. An object will float if the water it displaces has a mass greater than the object’s mass. It will sink if the water it displaces has a mass less than its own mass. But if an object displaces its own mass in water, it will neither float nor sink. Instead, it will remain suspended in the water because of what is called neutral buoyancy.

A goldfish has neutral buoyancy. A goldfish has a sac in its body called a swim bladder. Gases from blood vessels can diffuse into and out of the swim bladder. When the goldfish needs to rise in the water, for example, gases diffuse into the swim bladder and cause it to inflate. The swim bladder helps the goldfish maintain neutral buoyancy.

1. What is the purpose of this passage?

A to explain how a goldfi sh maintains neutral buoyancy

B to explain how to change the buoyancy of an object

C to convince people to buy goldfi shD to describe objects that fl oat and sink

2. What is the meaning of the word suspended in this passage?

F not allowed to attend schoolG stopped for a period of timeH weighed downI supported from sinking

3. What is buoyancy?

A a sac in a goldfi sh’s bodyB the ability to fl oatC the mass of an objectD an infl ated balloon

Passage 11. C2. I3. B

Question 1: Although “overthrow-ing the government” is a meaning of the word revolutionary, it is not the correct meaning of the word in the passage. There is no mention of gov-ernment in the passage. “Radically different” is also a meaning of the word revolutionary and is the correct answer.

Passage 21. A2. I3. B

Question 2: Answer choices F, G, and I are all correct meanings of the word suspended.However, both answer choices F and G can be eliminated because the passage does not discuss school attendance or mention stopping any activity for a period of time. The passage does discuss sinking and floating, and I is the correct answer.


Stand

ardized

Test Prep

aration

1. What is the pressure on the object when it is 100 m underwater?

A 1.0 MPaB 1.1 MPaC 1.5 MPaD 2.0 MPa

2. Based on the data in the graph, which of the following is the best estimate of the pressure at 250 m below the surface of the ocean?

F 1.7 MPaG 2.2 MPaH 2.6 MPaI 5.0 MPa

3. Which of the following statements best describes the relationship between the water pressure on an object and the depth of the object in the ocean?

A Water pressure increases as the depth increases.

B Water pressure decreases as the depth increases.

C Water pressure does not change as the depth increases.

D Water pressure has no predictable relationship to the depth.

1. Anna-Marie has a coil of wire. She uses a balance to fi nd that the wire has a mass of 17.8 g. She uses water displacement to fi nd that the volume of the wire is 2.0 cm3. Density is equal to mass divided by volume. What is the density of the wire?

A 0.11 g/cm3

B 8.9 g/cm3

C 19.8 g/cm3

D 35.6 g/cm3

2. Hussain rode his bike 30 km this weekend. What is this distance expressed in meters?

F 0.3 mG 300 mH 30,000 mI 300,000 m

3. Olivia purchased 21 tubes of oil paint at $3.95 per tube, which includes tax. What was the total cost of the 21 tubes of paint?

A $65.15B $82.95C $89.10D $93.50

4. Javi fi lled a container halfway full with water. The container measures 2 m wide, 3 m long, and 1 m high. How many cubic meters of water are in the container?

F 2 m3

G 3 m3

H 5 m3

I 6 m3

5. Pressure is equal to force divided by area. Jenny pushes a door with a force of 12 N. The area of her hand is 96 cm2. What is the pressure exerted by Jenny’s hand on the door?

A 0.125 N/cmB 0.125 N/cm2

C 8 N/cmD 8 N/cm2

The graph below shows the water pressuremeasured by a scientist at different depths in the ocean. Use the graph below to answer the questions that follow.

Read each question below, and choose the best answer.

INTERPRETING GRAPHICS MATH

2.5

2.0

1.5

1.0

0.5

0500 150

Depth (m)

200100

Water Pressure Versus Depth

250

Pres

sure

(M

Pa)

INTERPRETING GRAPHICS1. B2. H3. A

Question 2: To answer this ques-tion, students must extrapolate (or imagine) that the line in the graph continues up and to the right. Students should determine that the extrapo-lated line will cross the 250 m point somewhere just above 2.5 MPa. The only answer choice that is above and close to 2.5 MPa is H.

MATH1. B2. H3. B4. G5. B

Question 4: Students may be tempted to multiply the dimensions of the container to find the total volume of the container. However, the prob-lem clearly states that the container is only halfway full with water. There-fore, students must multiply 2 m, 3 m, and 0.5 m to find the number of cubic meters in the container. The correct choice is G.

CHAPTER RESOURCES


CRF • Standardized Test Preparation g

State Resources

For specifi c resources for your state, visit go.hrw.com and type in the keyword HSMSTR.

Chapter 7 • Standardized Test Preparation 203

in Action

in Action

Language ArtsAnalyze the story structure of “Wet Behind the Ears.” In your analysis, identify the intro-duction, the rising action, the climax, and the denouement. Summarize your analysis in a chart.

MathA Frisbee landed 10 m away from where it is thrown. The Frisbee was in the air for 2.5 s. What was the average speed of the Frisbee?

Science, Technology,

and SocietyStayin’ Aloft—The Story of the Frisbee®

In the late 1800s, a few fun-loving college students invented a game that involved toss-ing an empty tin pie plate. The pie plate was stamped with the name of a bakery: Frisbie’s Pies. So, the game of Frisbie was created. Unfortunately, the metal pie plates tended to develop sharp edges that caused injuries. In 1947, plastic disks were made to replace the metal pie plates. These plastic disks were called Frisbees. How do Frisbees stay in the air? When you throw a Frisbee, you give it thrust. And as it moves through the air, lift is created because of Bernoulli’s principle. But you don’t have to think about the science behind Frisbees to have fun with them!

Science Fiction “Wet Behind the Ears” by Jack C. Haldeman IIWillie Joe Thomas cheated to get a swim-ming scholarship. Now, he is faced with a major swim meet, and his coach told him that he has to swim or be kicked off the team. Willie Joe could lose his scholarship.

One day, Willie Joe’s roommate, Frank, announces that he has developed a new “sliding compound.” And Frank also said something about using the compound to make ships go faster. So, Willie Joe thought, if it works for ships, it might work for swimming.

See what happens when Willie Joe tries to save his scholarship by using Frank’s compound at the swim meet. Read “Wet Behind the Ears,” by Jack C. Haldeman II in the Holt Anthology of Science Fiction.

Science, Technology,

and Society

Teaching Strategy-- GENERAL

Go to an open area with your students. Have students throw a Frisbee® with different amounts of thrust, or have them vary the angle of attack when they throw their disk. Discuss Bernoulli’s principle and other aspects of lift. Have students attempt to throw a Frisbee without any spin (eliminating the angular momentum that gives the disk stability in flight). Compare a spinning Frisbee with a spinning top or a moving bicycle.

Science Fiction

BackgroundSports and science fiction may seem like an unlikely combina-tion, but Jack C. Haldeman II enjoys both. He has written science fiction stories, sports sto-ries, and stories such as “Wet Behind the Ears,” which is a bit of both! Before becoming a writer, Haldeman received a col-lege degree in life science and worked as a research assistant, a medical technician, a statisti-cian, a photographer, and an apprentice in a print shop.

Answer to Math Activity

The equation for average speed is:average speed � distance � timeaverage speed � 10 m � 2.5 s � 4 m/s

Answer to Language Arts Activity

Accept all reasonable answers. Students should make a chart that analyzes the story structure of ”Wet Behind the Ears.” The first column of their chart should list the parts of the story (introduc-tion, rising action, climax, and denouement). The second column should have a brief summary of what occurred in each part of the story.


To learn more about these Science in Action topics, visit go.hrw.com and type in the keyword HP5FLUF.

Check out Current Science®

articles related to this chapter by visiting go.hrw.com. Just type in the keyword HP5CS07.

Social StudiesScuba divers and other underwater explorers sometimes investigate shipwrecks on the bottom of the ocean. Research the exploration of a specific shipwreck. Make a poster showing what artifacts were retrieved from the shipwreck and what was learned from the exploration.

Alisha BrackenScuba Instructor Alisha Bracken first started scuba diving in her freshman year of college. Her first dives were in a saltwater hot spring near Salt Lake City, Utah. “It was awesome,” Bracken says. “There were nurse sharks, angelfish, puffer fish and brine shrimp!” Bracken enjoyed her experience so much that she wanted to share it with other people. The best way to do that was to become an instructor and teach other people to dive.

Bracken says one of the biggest challenges of being a scuba instructor is teaching people to adapt and function in a foreign environment. She believes that learning to dive properly is important not only for the safety of the diver but also for the protection of the under-water environment. She relies on science principles to help teach people how to control their movements and protect the natural environment. “Buoyancy is the foundation of teaching people to dive comfortably,” she explains. “Without it, we cannot float on the surface or stay off the bottom. Underwater life can be damaged if students do not learn and apply the concepts of buoyancy.”

Careers

BackgroundThe word scuba is an acronym that stands for self-containedunderwater breathing apparatus.The first scuba breathing device, known as the aqualung, was invented by Jacques Cousteau and Emile Gagnan in 1943. This invention allowed divers to move freely underwater for long periods of time.

Scuba diving has become a pop-ular form of recreation, with about one million people becoming certified divers every year. To rent scuba equipment, divers must be certified by an organization such as the Professional Association of Diving Instructors (PADI) or the National Association of Underwater Instructors (NAUI). Some organizations certify div-ers as young as 10 years old, while other groups have an age requirement of 12 years. In order to receive a certification, divers must take an open water diving course, which can last from three days to six weeks.

Answer to Social Studies Activity

Accept all reasonable answers. All students’ posters should identify a shipwreck, list or show some of the artifacts collected from the ship-wreck, and summarize what was learned by the exploration of the shipwreck.

Chapter 7 • Science in Action 205

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