39771 PIA FORCES MOTION IG - Infobaseusing ‘ragdoll physics’ has calculated the effect of...

Copyright © 2010 Films for the Humanities & Sciences® • www.films.com • 1-800-257-5126

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Physics in Action FORCES AND MOTION

Introduction This Instructor’s Guide provides information to help you get the most out of Forces and Motion, part of the five-part series Physics in Action. The contents of the guide will allow you to prepare your students before using the program and to present follow-up activities to reinforce the program’s key learning points.

Can the study of physics be fun? This clever five-part series answers “Yes!” by presenting essential facts, formulas, and laws of physics through real-world examples, illustrative animations, and a like-able field guide named Mr. Physics who makes complicated concepts easier to understand. End-of-section reviews are included throughout each program, and equations are worked out, step by step, on-screen.

The series includes the following titles: •Energy •ForcesandMotion •Planets,Stars,andGalaxies •ProcessesThatShapetheEarth •TheNatureofMatter

Learning Objectives After viewing the program, students will be able to: • Calculatespeed,distance,andacceleration• Understandvectorsandscalars• Understandtrajectoryandg-force• Definecontactforcesandaction-at-a-distanceforces• Understandtherelationofgravitytomassandweight

Instructor’s Guide

Physics in Actions FORCES AND MOTION Instructor’s Guide


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Educational StandardsBENCHMARKS FOR SCIENCE LITERACY STANDARDSThis program correlates with the following standards from BenchmarksforScienceLiteracy, by the American Association for the Advancement of Science, for grades 9 through 12. The Physical Setting: Motion• Althoughthevariousformsofenergyappearverydifferent,eachcanbemeasuredinawaythat

makes it possible to keep track of how much of one form is converted into another. Whenever the amount of energy in one place diminishes, the amount in other places or forms increases by the same amount.

• Thechangeinmotion(directionorspeed)ofanobjectisproportionaltotheappliedforceandinversely proportional to the mass.

• Wheneveronethingexertsaforceonanother,anequalamountofforceisexertedbackonit.• Theenergyofwaves(likeanyformofenergy)canbechangedintootherformsofenergy.• Anyobjectmaintainsaconstantspeedanddirectionofmotionunlessanunbalancedoutside

force acts on it. The Physical Setting: ForcesofNature• Gravitationalforceisanattractionbetweenmasses.Thestrengthoftheforceisproportionalto

the masses and weakens rapidly with increasing distance between them.• Electricforcesactingwithinandbetweenatomsarevastlystrongerthanthegravitationalforces

acting between the atoms. At larger scales, gravitational forces accumulate to produce a large and noticeable effect, whereas electric forces tend to cancel each other out.

• Attheatomiclevel,electricforcesbetweenelectronsandprotonsinatomsholdmoleculestogetherand thus are involved in all chemical reactions.

The Mathematical World: SymbolicRelations• Sometimestherateofchangeofsomethingdependsonhowmuchthereisofsomethingelse

(astherateofchangeofspeedisproportionaltotheamountofforceacting).• Symbolicstatementscanbemanipulatedbyrulesofmathematicallogictoproduceotherstate-

ments of the same relationship, which may show some interesting aspect more clearly. • Symbolicstatementscanbecombinedtolookforvaluesofvariablesthatwillsatisfyallofthem

at the same time. • Tables,graphs,andsymbolsarealternativewaysofrepresentingdataandrelationshipsthatcan

be translated from one to another. • Whenarelationshipisrepresentedinsymbols,numberscanbesubstitutedforallbutoneofthe

symbols and the possible value of the remaining symbol computed. Sometimes the relationship may be satisfied by one value, sometimes by more than one, and sometimes not at all.

SOURCE: BenchmarksForScienceLiteracy, by The American Association for the Advancement of Science. Copyright 1993, 2009byTheAmericanAssociationfortheAdvancementofScience.UsedbypermissionofOxfordUniversityPress,Inc.



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ENGLISH LANGUAGE ARTS STANDARDS The activities in this instructor’s guide were created in compliance with the following standards from NationalStandardsfortheEnglishLanguageArts, from the National Council of Teachers of English.• Studentsadjusttheiruseofspoken,written,andvisuallanguage(e.g.,conventions,style,vocabulary)

to communicate effectively with a variety of audiences and for different purposes. • Studentsemployawiderangeofstrategiesastheywriteandusedifferentwritingprocesselements

appropriately to communicate with different audiences for a variety of purposes. • Studentsconductresearchonissuesandinterestsbygeneratingideasandquestions,andbyposing

problems.Theygather,evaluate,andsynthesizedatafromavarietyofsources(e.g.,printandnon-printtexts,artifacts,people)tocommunicatetheirdiscoveriesinwaysthatsuittheirpurposeandaudience.

• Studentsuseavarietyoftechnologicalandinformationresources(e.g.,libraries,databases, computernetworks,video)togatherandsynthesizeinformationandtocreateandcommunicateknowledge.

• Studentsusespoken,written,andvisuallanguagetoaccomplishtheirownpurposes(e.g.,forlearning,enjoyment,persuasion,andtheexchangeofinformation).

SOURCE: Standards for the English Language Arts, by the International Reading Association and the National Council of Teachers of English. Copyright 1996 by the International Reading Association and the National Council of Teachers of

English. Reprinted with permission.

TECHNOLOGY STANDARDSThe activities in this instructor’s guide were created in compliance with the following standards from TheISTENationalEducationTechnologyStandards(NETS•S)andPerformanceIndicatorsforStudents. • Creativity and Innovation: Students demonstrate creative thinking, construct knowledge, and

develop innovative products and processes using technology. • Research and Information Fluency: Students apply digital tools to gather, evaluate, and use

information. • CriticalThinking,ProblemSolving,andDecisionMaking: Students use critical thinking skills

toplanandconductresearch,manageprojects,solveproblems,andmakeinformeddecisions using appropriate digital tools and resources.

SOURCE: © 2007 The International Society for Technology Education. Reprinted with permission.



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Program Overview InNewYorkCity,therearemanywaystotravel.Ofcourse,it’saloteasierifyou’reabird.UsingtheBig Apple as a living laboratory, this program addresses speed and distance using a pigeon, a taxi, and a tour boat. Additional situations such as the deployment of a Mars rover, a zero-G flight in NASA’s WeightlessWonder,awalkonaconveyorbeltandacruisingaircraftcarrier,andjugglingontheEarthand around the Solar System provide opportunities to study the mechanics of velocity and acceleration as well as contact forces and forces that act at a distance. Vector algebra is demonstrated throughout.

Main TopicsChapter 1: Calculating Speed and DistanceUsingtheexamplesofapigeon,ataxi,andatourboatcirclingManhattan,theprogrambeginsbyexplaining how to calculate speed and distance, taking into account both path length and displace-ment. Also covered: dimensions, units, and conversion factors.

Chapter 2: Speed and AccelerationThe deployment of a Mars rover is used to illustrate concepts of acceleration and speed. Also covered: using a diagram, chart, or graph to track position over time.

Chapter 3: Vectors: Motion in the Three DimensionsHere Mr. Physics explains vectors and scalars, and how they are used to describe, in mathematical terms, movement and direction.

Chapter 4: Accelerated MotionsNASA’s“WeightlessWonder”—akatheVomitComet—isfeaturedinthisdiscussionoftrajectory,parabolas, and g-force.

Chapter 5: ForcesThis section discusses contact forces, such as friction and tension, and action-at-a-distance forces, such as electromagnetism. The relation of gravity to mass and weight is explained as Mr. Physics weighsajugglingpinonEarth,theMoon,andJupiter.Pointmassandforce-bodydiagramsarealsocovered.

Chapter 6: Forces and AccelerationsThe program’s final section explores the relationship between forces and motion, and points out that understanding the law of conservation of momentum is useful for modeling the results of impacts and explosions.



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Fast Facts • TheconstantaveragespeedofaMarsroverheadingtowarditsdestinationisanamazing31,500

meters per second.

• Scientistsusetheterm‘acceleration’foranychangeinspeed,whetherit’sspeedinguporslowingdown.

• Scalarsarequantitieswhichcanbedescribedintermsofmagnitudeornumericalvalue,suchastime, mass, and temperature. Vectors are quantities which are described by both a magnitude and a direction.

• Theconceptsof‘distance’and‘displacement’aresimilar.Butdistanceisascalar quantity that describeshowmuchgroundanobjecthascoveredduringitsmotion;anddisplacementisavector quantitythatdescribesanobject’soverallchangeinposition.

• Aspartofastronauttraining,NASAusesspecialaircraftcapableofprovidinganearlyweightlessenvironment. A state of free fall is achieved by following a flight path that is elliptical in relation toEarth’scenter;thecraftdoesnotexertanyg-forcesontheastronauts.NASAcallsthisaircraftthe‘WeightlessWonder,’butforreasonsyoucanimagine,it’smorecommonlyknownasthe‘VomitComet.’

• Whetherit’sacannonball,astreamofwater,oraplanethatcutsitsengines,objectshurtledthroughtheairwillalltakeroughlythesamepath(theshapeofthatpathiscalledaparabola).

• Creatorsofcomputergamesandspecialeffectsinmoviesusetheprinciplesofphysicstocreaterealistic-looking explosions. Smoke, flames, and clouds of debris act a lot like their real-life counter-parts due to software that calculates speed and direction. When virtual people fall over dead, software using‘ragdollphysics’hascalculatedtheeffectofgravityonthebody,andhowdifferentbodypartswould move as the body slumps or falls down.

• Theideathatafreeparticletakesthequickestpathbetweenitsstartingandendingpointsiscalledthe‘principleofleasttime.’AncientGreekandArabscientistsstatedthisprincipleforpathsofraysof light. In the 20th century Albert Einstein demonstrated that a parabola could be the shortest path between two points when space and time were curved in the presence of gravity.

• Wecategorizeforcesasbeingeither‘contact’(wheretheinteractingobjectstouch)or‘action-at-a-distance’(wheretheydon’t).Butifwelookdeepintothesmall-scalestructureofmatter,theconceptofobjectstouchinglosesitsmeaning.Actually,allcontactforcesaretheresultofelectromagnetism,which is an action-at-a-distance force.



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Vocabulary Terms acceleration: The vector which gives the direction of, and the instantaneous rate at which velocity changes with time.

action-at-a-distance-force: A fundamental force of nature that is seemingly transmitted over emptyspace;thatis,theinteractingobjectsdonottouch.Examplesincludeelectromagneticforces,theweakforce(changessubatomicparticlesfromonekindtoanother),thestrongforce(holdstheatomicnucleustogether),andgravity.

average speed: The straight-line distance between the end-points of a motion, divided by its duration in time.

contact force: A nonfundamental force of nature that can be traced to the physical touching of two objects.Examplesincludefriction,fluidresistance,tension,springforce,andbuoyantforce.

dimension: The type of physical property that a number or variable represents. Examples include length, mass, and time.

displacement: Thevectorthatjoinstwosubsequentpositionsofanobject;anobject’soverallchange in position.

distance: A scalar quality which refers to the extent or amount of space between points.

force: An influence that, if applied to a free body, results in an acceleration of that body.

force-body diagram: A technique of making a simplified drawing of the individual force vectors actingonanobject.

g-force: Aforceactingonabodyastheresultofaccelerationorgravity;aforceexperiencedbyabodywhichisitsaccelerationrelativetofree-fall.(Technically,g-forceisnotaforce,butanacceleration.)

inertia: The property of matter by which it retains its state of rest or its velocity along a straight line so long as it is not acted upon by an external force.

parabola: A geometrical shape consisting of a single bend and two lines going off to an infinite distance.Aparabolaisthetrajectorythatmostobjectstakeastheyflyunpoweredthroughtheair.

path length: Thelengthoftheactual,physicalpathtraversedbyanobject(asopposedtothestraight-linedistancebetweentheendpoints).



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point mass: Ahypotheticalobjectinwhichallthephysicalbulkisconcentratedinatiny,point-sized location.

scalar: Aquantitywhichisdescribedbymagnitude(ornumericalvalue)alone;anumberoralgebraic symbol that has a size, but no direction. Time, mass, and temperature are all examples of scalars.

trajectory: Thepathofanobjectmovingthroughspace.

vector: A quantity that is fully described by both magnitude and direction.

velocity: The vector which gives the directon of and the instantaneous rate at which the displace-mentofanobjectchangeswithtime.

Pre-Program Discussion Questions1.Whatdoyouthinkisthedifferencebetween‘distance’and‘displacement’?2. When launching a missile into space, do scientists simply point it in a certain direction? With no one

steering, what factors do you think come into play to ensure a Mars rover makes it from the launch-ing pad to Mars?

3. What is the difference between velocity and acceleration?4. What are “forces at a distance”?5.Whyistimeconsideredtobeadimension?

Post-Program Discussion Questions1. What is path length? What is displacement?2. What is the difference between a vector and a scalar?3. After viewing the program, can you explain the difference between distance and displacement?4. What is g-force?5.Whatisthelawofconservationofmomentum?



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Student ProjectsThe basic idea behind quantum mechanics is that when an action is performed on a certain •particle,anotherparticlewithwhichisit‘entangled’willrespond—evenifthetwoparticlesaremilesapart.UsingthelibraryandInternet,researchandreportonquantummechanics.WhatdidEinsteinmeanwhenhecalledit‘spookyaction-at-a-distance’?Whateverydayapplicationsdoscientistsforeseeforquantummechanics?(VisitWebsitessuchaswww.livescience.com,www.sciencentral.com, and www.popsci.com [PopularScience]forideasandinformation.)

Usingtermssuchasg-force,acceleration,velocity,andfreefall,createanillustratedreport •explaining the physics behind a roller coaster ride, cliff diving, and skateboarding.

Create a chart with information on contact forces. Columns should include the name of the •force(e.g.,‘frictional’);itssymbol(e.g.,F

f);howitworks(e.g.,whentwosurfacesareinclose

contact,themoleculesofeachpullandpushlaterallyagainsteachother);andsomethingsthatthisforcedoes(e.g.,allowscarbrakestowork,enablesustowalkinsteadofstayinginplace).

•



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Assessment Questions1. For a taxi to drive from one corner of Central Park to the other, it will have to stay on the roads.

If we want to calculate the taxi’s average speed along its route, we use the taxi’s _____ rather than displacement.

a)accelerationdividedbyamountoftimetraveled b)amountoftimetraveleddividedbyacceleration c)pathlength d)pathspeed

2. Average acceleration is change in speed divided by change in _____. a)averagespeed b)time c)velocity d)trajectory

3.‘80mileseast’isanexamleofa[scalar / vector].‘256bytes’isanexampleofa[scalar / vector]. ‘150calories’isanexampleofa[scalar / vector].

4. True or False? A cannonball, a stream of water, and a plane that cuts its engines will hurtle throughtheairineitherashallowcurveorastraightline,dependingontheweightoftheobject.

5.Whatconcepthelpsphysicistscalculatethemotionofanobjectmovingfromplanettoplanet,and thus changing its weight?

a)Pointmass b)Aforce-bodydiagram c)Conservationofmotion d)Action-at-a-distanceforce

6.Fluidresistanceisanexampleofa(n)[contact force / action-at-a-distance force]. Electromag-netismisanexampleofa(n)[contact force / action-at-a-distance force]. Tension is an example ofa(n)[contact force / action-at-a-distance force]. Gravity is an example of a [contact force / action-at-a-distance force].



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7. [Mass / weight] is constant, but [mass / weight] is proportional to gravity.

8.Thedefinitionof‘momentum’is‘masstimes_____.’ a)weight b)speed c)velocity d)inertia

9.TrueorFalse?AccordingtotheLawofConservationofMomentum,iftwoobjectscollideintheabsence of outside force, momentum would not be lost.

10. Net forces cause _____. a)conservationofmomentum b)speed c)velocity d)acceleration



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Assessment Questions Answer Key1. For a taxi to drive from one corner of Central Park to the other, it will have to stay on the roads.

If we want to calculate the taxi’s average speed along its route, we use the taxi’s _____ rather than displacement.

a)accelerationdividedbyamountoftimetraveled b)amountoftimetraveleddividedbyacceleration c)pathlength d)pathspeedA:(c)pathlength

2. Average acceleration is change in speed divided by change in _____. a)averagespeed b)time c)velocity d)trajectoryA:(b)time

3.‘80mileseast’isanexamleofa[scalar / vector].‘256bytes’isanexampleofa[scalar / vector]. ‘150calories’isanexampleofa[scalar / vector].

A:‘80mileseast’isanexamleofavector.‘256bytes’isanexampleofascalar.‘150calories’isanexampleofascalar.

4. True or False? A cannonball, a stream of water, and a plane that cuts its engines will hurtle throughtheairineitherashallowcurveorastraightline,dependingontheweightoftheobject.

A:False.Whetherit’sacannonball,astreamofwater,oraplanethatcutsitsengines,objectshurtledthroughtheairwilltakeroughlythesamepath.Theshapeofthatshapeiscalledaparabola.

5.Whatconcepthelpsphysicistscalculatethemotionofanobjectmovingfromplanettoplanet,and thus changing its weight?

a)Pointmass b)Aforce-bodydiagram c)Conservationofmotion d)Action-at-a-distanceforceA: (a) Point mass



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6.Fluidresistanceisanexampleofa(n)[contact force / action-at-a-distance force]. Electromag-netismisanexampleofa(n)[contact force / action-at-a-distance force]. Tension is an example ofa(n)[contact force / action-at-a-distance force]. Gravity is an example of a [contact force / action-at-a-distance force].

A:Fluidresistanceisanexampleofacontact force.Electromagnetismisanexampleofanaction-at-a-distance force.Tensionisanexampleofacontact force.Gravityisanexampleofanaction-at-a-distance force.

7. [Mass / weight] is constant, but [mass / weight] is proportional to gravity.A: Massisconstant,butweight isproportionaltogravity.

8.Thedefinitionof‘momentum’is‘masstimes_____.’ a)weight b)speed c)velocity d)inertiaA:(c)velocity

9.TrueorFalse?AccordingtotheLawofConservationofMomentum,iftwoobjectscollideintheabsence of outside force, momentum would not be lost.

A:True.

10. Net forces cause _____. a)conservationofmomentum b)speed c)velocity d)accelerationA:(d)acceleration



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Additional ResourcesScienCentralScienceVideos,ScienceNewswww.sciencentral.com

Physics.orgYourguidetophysicsonthewebwww.physics.org

Institute of Physics.orgwww.iop.org

Scientific Americanwww.sciam.com

Popular Sciencewww.popsci.com

LiveSciencewww.livescience.com

ScienceDailyYoursourceforthelatestresearchnewswww.sciencedaily.com



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39771 PIA FORCES MOTION IG - Infobaseusing ‘ragdoll physics’ has calculated the effect of...

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