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More curriculum can be found in Pearson Addison Wesley‘s Conceptual Physics Laboratory Manual: Activities · Experiments · Demonstrations · Tech Labs by Paul G. Hewitt and Dean Baird. ISBN: 0321732480

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CONCEPTUAL PHYSICS: Hewitt/Baird Tech Lab

Linear Motion Motion Graphing Simulation

Motivating the Moving Man PurposeTostudyone‐dimensionalmotionthroughtheuseofacomputersimulationApparatuscomputerPhETsimulation:“MovingMan”(availableathttp://phet.colorado.edu)

Setup1.Turnthecomputeron,logonandallowittocompleteitsstartupcycle.

2.FindandstartthePhETSimulationsandruntheMovingMansimulation.Askyourinstructorforassistanceifneeded.

3.Locatethetime‐scaleexpansionbutton.Timeisthehorizontalaxis,nottheverticalaxis.Usethetimescaleexpansionbuttontoexpandthetimeaxissothatonly10secondscanbeseen.

4.Findandusethebuttonsthatwilldeletethevelocityvs.timeandaccelerationvs.timegraphs.Youareleftwithonegraph:positionvs.time.Anditshorizontalaxisnowrunsfromonly0to10seconds.

5.SetthecomputerasideandreadtheDiscussionsectionbelow.WhenyouhavefinishedreadingtheDiscussion,continuewiththeactivity.

DiscussionThesimulationprovidesuswithasimpleinterfacewecanusetostudymotiongraphs.Specifically,wecancontroltheposition,velocity,andaccelerationofanobjectandseethegraphsofposition,velocity,andaccelerationofthatobject.

Thesimulationallowsustomanuallycontroltheobjectbydraggingit.Wecanalsodragaposition“slider”control.

Moreimportantly,wecansetinitialconditionsfortheobjectthenletitsmotionproceed.Wecanpausethemotion,andthemotionislimitedinspacebythewalls.

ProcedureStep1:Completethematchingexerciseonthenextpage.Thenamesofmanyobjectsandbuttonsarelisted.Drawalineconnectingthenameofeachobjectorbuttontotheobjectorbutton,itself.YourscreenandFigure1shouldbeverysimilarinthatonlythepositionvs.timegraphisvisibleandthatthehorizontal(time)scalerunsfrom0to10seconds.PhETsimulationsarerevisedfromtimetotime,sosomeelementsofthescreenlayoutmayhavechanged.

Step2:ManualMana. Clickonthemananddraghiminthepositivedirection(towardthehouse)atasteadyrateof

1m/stothebestofyourability.Yourgraphwon’tbeperfect(limitationsofthecomputer’sinterfacepreventthis),buttrytomovethemanassmoothlyasyoucanat1m/s.

b. Whilethegraphisstillonthescreen,clicktheon‐screenbuttontoshowthevelocityvs.timegraph.Thisgraphplotsthevalueofthevelocityastimepasses.Clearthegraphsandtryagain.Movethemanmanuallyfrom0to10metersin10seconds—assmoothlyaspossible—at1m/s.Thesimulation’s“stopwatch”readingindicatestime.


c. Sketchtheresultingpositionvs.timeandvelocityvs.timegraphsonthegraphspageattheendofthiswrite‐up.

Step3:ProgrammedMana. Makesurethepositionandvelocitygraphsareshowing(withthetimescalesetfrom0to10

seconds)andtheaccelerationgraphishidden(deleted).Clearthegraphs.

b. Settheinitialpositionofthemanto0m.(Usethesliderortypeitintothevaluebox.)

c. Settheinitialvelocityofthemanto+1.0m/s.(Usethesliderortypeitintothevaluebox.)

d. Clickanon‐screenGobuttonandobservetheresultingmotiongraphs.Sketchbothgraphs(positionvs.timeandvelocityvs.time)onthegraphspageattheendofthelab.

e. Clearthegraphs.Settheinitialvelocityofthemanto+2.0m/sandrunthesimulationagain.Themotionendswhenthemanhitsthewall.Stopthesimulationwhenthatoccurs.Disregarddatafromthewallimpactandbeyond.Describetwodifferencesinthepositionvs.timegraph.(Hints:rise/run;duration.)

f. Addlinestoyourprevioussketchrepresentingthe+2.0m/smotion.Besuretolabelbothlinesnowplotted.Anddonotincludeplotteddataaftertheimpactwiththewall.

g. Addandlabeladashedlinetothegraphsshowingtheresultiftheinitialvelocityofthemanwere+5m/s.(Note:donotcarrythisprocedureoutonthesimulation.)

h. Describetwochangesthatoccuronthevelocityvs.timegrapheachtimeyoumaketheinitialspeedofthemangreater.

Step4:BackUptheChooChooa. Clearthegraphs.Theaccelerationgraphisstillhidden.

b. Settheinitialpositionofthemanto0m.Settheinitialvelocityofthemanto–2.0m/s.

c. Runthesimulationandobservethemotiongraphs.Again,themotionendswhenMovingMancrashesintothewall,sostopthesimulationwhenthathappens.SketchthegraphsonthesamesetofaxesusedforStep3,disregardingdatafromthewallimpactandbeyond.

d. Clearthegraphs.Settheinitialvelocityofthemanto–4.0m/sandrunthesimulation.Describetwodifferencesinthepositionvs.timegraph,andaddalinetoyourprevioussketchrepresentingthe–4.0m/smotion.Besuretolabelbothlinesnowplotted.

e. Addandlabeladashedlinetothegraphsshowingtheresultiftheinitialvelocityofthemanwere–10m/s.(Note:Donotcarrythisprocedureoutinthesimulation.)


f. Describetwochangesthatoccuronthevelocityvs.timegrapheachtimeyoumaketheinitialspeedofthemangreater(fasterinthenegativedirection).

g. Clicktheon‐screenbuttontoshowtheaccelerationvs.timegraph.Whatdoestheaccelerationvs.timegraphtellyouaboutthemotionsobservedsofar?

Step5:Pickin’UpthePace

a. Clearthegraphs.Allthreegraphsarenowshowing.

b. Settheinitialpositionofthemanto0m.Settheinitialvelocityofthemanto0m/s.Settheaccelerationofthemanto+0.5m/s2.

c. Runthesimulationandobservethemotiongraphs.Sketchthegraphsonthegraphpage.

d. Whatdoestheaccelerationvs.timegraphtellyouaboutthenatureofthismotion?(Donotrefertonumericalvaluesinyourresponse.)

Step6:OnceMore,WithFeelinga. Settheinitialpositionofthemanto0m.Settheinitialvelocityofthemanto0m/s.Setthe

accelerationtothemanto+2.0m/s2.

b. Runthesimulationandobservethepositionvs.timegraph.

i. Sketchthegraphonthesamesetofaxesaspart5.

ii. Howisthispositionvs.timegraphdifferentfromtheoneplottedinpart5above?

c.Howdoesthevelocityvs.timegraphdifferfromtheoneproducedinpart5above?

d.BasedonwhatyoulearnedinSteps5and6,sketchallthreemotiongraphsthatthemanwouldproduceifhestartedatx=0m,v=0m/s,anda=–1m/s2.Don’tactuallycarrythisprocedureoutonthesimulation.Simplysketchwhatyouthinkitshouldbebasedonyourexperience.


Step7:RoundTripa. Withallthreegraphsshowing,adjustthescaleofthetimeaxistodisplay20seconds.

b. Settheinitialpositionofthemanto–10m.Settheinitialvelocityto+3.0m/s.Settheaccelerationto–0.3m/s2.

c. Runthesimulationandobservethemotiongraphs.Sketchthegraphsonthegraphspage.

d. Selectthebestdescriptionsofthevelocityandaccelerationofthemanattheapexofhismotion(whenhe’sisfarthestfromhisstartingpoint).Chooseonedescriptionoftheman’svelocityandonedescriptionoftheman’sacceleration.Feelfreetousetherewindandforwardstepfeaturesofthesimulation.

__The velocity is positive: the man is moving to the right. __The velocity is zero: the man is at rest. __The velocity is negative: the man is moving to the left.

__The acceleration is positive: the man’s velocity is increasing. __The acceleration is zero: the man is maintaining constant velocity. __The acceleration is negative: the man’s velocity is decreasing.

e. Youoverhearaclassmatetellingsomeonethatit’spossibleforanobjecttobeatrestandacceleratingatthesametime.Whatdoyouthinkofthatstatement?

Step8:TheSloshingManPuzzlea. Clearallgraphs.Setthepositionnear–2m.Clickanddragthemanfrom–2mto+2mwith

uniformmotionandlethimrest.Thendraghimfrom+2mto–2mwithuniformmotionandlethimrest.Repeat.Theresultingpositionvs.timegraphshouldlooksimilartotheplotbelow.Don’tworryaboutthetimetoomuch;what’simportantismovingthemanoneway,thenresting,thenmovinghimtheotherway,thenresting.Yourlineswon’tbeasstraight,andthe“corners”ofyourgraphwillberounderthanthosedepictedbelow.

b. Examinethesectionoftheplotenclosedinthedashedbox.Thevelocityvs.timegraphhasapatternsimilartotheoneshownbelow.Unlikethetime‐alignedgraphsinthesimulation,thisgraphmayhavebeenshiftedhorizontally.Drawaboxtoenclosethesectionofthevelocitygraphthatcorrespondstotheboxedsectionofthepositionvs.timegraphabove.

Figure 2. Ideal Position vs. Time for Sloshing Man

Figure 3. Ideal Velocity vs. Time Segment for Sloshing Man


c. Theaccelerationvs.timegraphhasapatternsimilartotheoneshownbelow.Again,thisgraphmayhavebeenshiftedalongthetimeaxis.Anditisnotnecessarilytoscale.Drawaboxtoenclosethesectionoftheaccelerationgraphthatcorrespondstotheboxedsectionofthepositionvs.timegraphabove.

d. SketchthevelocityandaccelerationplotsinthespacebelowthepositionplotinFigure5below.

e. MatchthephrasesbelowtothemotionillustratedinFigure5.UsepointsA,B,C,orD,orsegments(e.g.,AB,BD).

Sustained positive velocity _______ Sustained negative velocity _______ Rest _______

Positive acceleration to start motion _______ Positive acceleration to stop motion _______

Negative acceleration to start motion _______ Negative acceleration to stop motion _______

Figure 4. Ideal Acceleration vs. Time Segment for Sloshing Man

Figure 5. Motion Graph Segment for Sloshing Man