Chapter 2-Glencoe TextPhysics (A) Winter, 2010-2011

NOTE: Write down the slides highlighted in YELLOW

Standards of Measurement

Objectives

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Accuracy and PrecisionTwo types of measuring systemsReview of DecimalsReview/Intro. of the Metric SystemScientific NotationData RepresentationPractice!

Are we measuring Accurately or Precisely?

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Accuracy Precision

WE WANT MEASUREMENTS TO BE BOTH!

Two Types of Meas. Systems

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• METRIC or SI Units is structured on a base unit for a certain measurement:• Length = meter• Volume = liter• Mass = gram• Temperature = ° Celsius

• STANDARD or ENGLISH system has no structure?• Used in USA only• Contains feet, inches, gallons, pounds, Fahrenheit

What Are We Going To Measure?

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DISTANCE (LENGTH)-meter is your base unit Ex. Length of a tree branch = 1.5 meters Length of this room = 8 meters

VOLUME-liter is your base unit Ex. 2 Liter Mountain Dew Bottles Ex. 500 milliliter Aquafina water bottle

MASS –gram is your base unit Ex. Mass of sugar in 12 oz. can of Mountain Dew: 46

grams Ex. Mass of Ping pong ball = 2.5 grams

DENSITY-Mass per unit volume of an object Calculated by Mass/Volume Ex. H2O = 1.0 g/cm3

TEMPERATURE-How “hot” something is Ex. Body Temperature 38 °C Ex. Engine Exhaust Temperature 700 °C

TIME-second is your base unit

How would you measure the distance from your house to

the mall?

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Let’s say you live 10 miles from the mallFirst, convert to metric: 10 miles = 16093 metersBut 16093 meters is huge!So add a prefix onto the base unit to make it easier to

manage:16093 meters = 16.093 kilometers (or 16.1 if rounding)

Saying “I live 16.1 kilometers from the mall” is a lot easier, eh?!

Review of Decimals

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If decimal is missing, we need to add it. Proper lingo is to add .0 to number

The .0 is ALWAYS added AFTER the last digit provided for the number

Ex. 1 689 = 689.0 with decimalEx. 2 2543219 = 2543219.0 with decimalEx. 3 0000000039 = 0000000039.0 with decimal It’s a good habit to put in the decimal place, if it isn’t

thereEx. 689 = ____________ with decimalEx. 6.89 = ____________ already has decimal

Let’s practice!

So, how does the Metric System work?

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Move the decimal point one place for each “step” desired

Ex. Change meters to centimeters1 meter = 10 decimeters = 100 centimeters1.0 meter = 10.0 decimeters = 100.0

centimetersMake your Metric Box Chart Flashcard!

kilo (k)hecto

(h)deca (da)

Base Units

meter (m)

gram (g)

liter (l)

deci (d)centi (c)

milli (m)

Move decimal to RIGHTMove decimal to LEFT

Metric Conversions Recipe

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Step 1: Put in the decimal place, if it isn’t there– Ex. 689 = ____________ with decimal

– Ex. 6.89 = ____________ already has decimalStep 2: Determine what you are converting

FROM and going TO– FROM: ________________

– TO: ________________Step 3: Use your Box Chart to move the

decimalStep 4: Write number and units and Circle

Your Answer!

Metric System Summary

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Base Units: meter, liter, gramPrefix added to base to make new numbersMetric system is based on powers of 10Each “step” is 1 decimal place to the right or

leftConverting to the right, moves the decimal to

right, and vice versa

kilo hecto deca

Base Units

metergramliter

deci centi milli

Move decimal to RIGHTMove decimal to LEFT

Metric Conversion

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Let’s practice together:#1 750 ml = _______ L

#2 234.5 kg = _________ mg

#3 2400 hg = _________ dg

#4 2.4 hg = ___________ dagNow, you practice!

Scientific Notation

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A way scientists write really big or really small numbers

It has two ways to be written:Scientific Notation Form: 4.6542 X 108 mExpanded Form: 465,420,000 m

Let’s break down the pieces to Scientific Notation: 4.6542 X 108 m

ONE DIGIT FROM 1-9

ANY AMOUNT OF DIGITS AFTER DECIMAL POINT

BIG X FOR “TIMES”

WE SAY “10 TO THE EIGHTH METERS”

Scientific Notation

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How Does It Work?Just like your Box Charts, but you either write

it as Scientific Notation, or Expanded FormEx. 1000 (g) (Expanded Form) = 1X103 (g) (Scientific Notation Form) = 1 (kg) (Simplified Conversion)Two Rules to follow

Scientific Notation

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Rule #1: When moving the decimal to the LEFT, the exponent for Scientific Notation is = number of places moved

Ex. 100000 Decimal moves 5 places to the left, so Scientific Notation Form = 1X 105

NOTE: Exponent = 5, and there are 5 zeros to the LEFT of decimal in original number

So, you can simply count the number of zeros to get exponent

Ex. 4000000 = ___________________

Scientific Notation

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Rule #2: When moving the decimal to the RIGHT, the exponent for Scientific Notation is = number of places moved. But when you move to the right, the nonzero is now part of the move.Ex. 0.000000000002 Decimal moves 12 places to the

right, so Scientific Notation Form = 2 X 10-12

NOTE: Exponent = 12, BUT there are 11 zeros to the RIGHT of decimal in original number. So the exponent is always ONE MORE than the number of zeros in original number

Ex. 0.006 (l) = ___________________

Let’s Practice!

How Can We Summarize our Measurements?

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• Graph them: (picture is worth a 1000 words….)• Plot them: (best way to see relationships)• Table results: (best way to summarize multiple

results)• Make a Concept Map: (best way to relate

measurements to other branches or topics in science)

• Make a Model: (what is better than a Mini-Me?)

Graphs

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BAR GRAPHSPIE GRAPHS

Graphs Continued

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Tables

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Exhaust Emissions Data (g/hp-hr)Component 1760 RPM 2100 RPM

HC (Total Unburned Hydrocarbons) 0.5 0.82NOx (Oxides of Nitrogen as NO2) 4.36 5.45CO (Carbon Monoxide) 1.91 3.11PM (Particulate Matter) 0.25 0.25SO2 (Sulfur Dioxide) 0.61 0.62CO2 (Carbon Dioxide) 500 510N2 (Nitrogen) 2400 2900O2 (Oxygen) 190 330H2O (Water Vapor) 180 190

Models

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Used when testing parts is too much $$Computer Simulated Models allow STEM folks

to move different levers/push buttons and evaluate outcomes…with little money invested

Can you name some models used in Science?

GE AIRCRAFT ENGINE TESTING

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Variables-What are They?

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The Control: The standard by which test results are comparedRemember accuracy and precision? The control is the bullseyeEx. Human Body Temp = 98.6 °F, Highway

Speed Limit = 70 mph, Independent and Dependent: Who’s Who?

Algebra I explains why (slope-intercept form)Let’s look at an X-Y plot if you don’t have Algebra

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Variables-What are They?

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Y AX

ISX AXIS

Y-axis goes up

and DOWN.

He is DEPENDE

NT Variable

X-axis is INDEPENDENT Variable

Variables-What are They?

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So, when you analyze an X-Y Plot:DEPENDENT VARIABLE = Y-AXIS TITLEINDEPENDENT VARIABLE = X-AXIS TITLE

Where do you put the control?Sometimes, on the plotSometimes, it’s a number NOT on the plot (i.e.

off the charts!)

LET’S GO MEASURE STUFF!

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