physics 12 unit: conservation of energy – lab #1

Physics12Unit:ConservationofEnergy–Lab#1

Mr.Ostoforov RevisedApril2,2014 Lab-Kinemeatics&EnergyPart1&2v.3.docx

Groupsof3:onemeasurer,onetimer,andonereleaser.ObjectiveBytheendofthislabsession,youwillbeabletounderstandthePrincipleofConservationofEnergyaswellasbuilduponyourcurrentunderstandingofKinematics(motion).MaterialsRequired

• Bench/RetortStand• UtilityClamp• StopWatch

• Track(4-5Sections)• WeightScale• MetreStick/TapeMeasure

• HotWheelsCar• Tape• BlankPaper

SetupUse the bench stand to support the track andsecurewith tape.Tape theotherendof the tracktothetopoftablemakingsuretoleave3–4inchesfromtheendof the track to theendof the table.Next,performsometestrunstogetafeelforhowtheexperiment isgoing towork.Place thecaronthe track at your desired height and observeroughly where the car lands on the floor oncereleased.Nowtapetheblanksheetofpapertothefloorsoitisroughlycenteredwherethecarlanded.Procedure-IMPORTANTREADTHISFIRST!For thisexperimenttobesuccessful, theaccuracyandprecisionofyourmeasurements isvery important. In order to help mitigate some of these errors you will be required tocomplete five (5) identical runs at the same exact height. Then you will calculate theaverageofthesetrials.Note:Ifyouhavearunthatseems‘outofplace’donotusethisintheaveragecalculation.Insteadmakenoteofthisinyourreportandredotherun.Fortheentiretyofthislabwewillignorefrictionallossesandairresistance.Measurements

1) Usingthescaleprovidedmeasurethemassofyourcarinkilograms(kg).RecordthismeasurementontheDiagramonthefollowingpage.Recall1kg=1000grams.

2) Markyourstartingpositiononthetrackusingasmallpieceoftape(thisistomakesure you release the car at exactly the same point each time. Next measure thisheight(h1)inmetersandrecorditontheDiagram.

YourName:_____________________Partner’sName:_____________________

_____________________Block:______



3) Nextmeasuretheheightofthetable(h2) inmetersandrecordthisnumberontheDiagrambelow.

4) Nowyoucanstartyourruns.Priortostarting,assigneachgroupmemberaspecificrole:releaser,measurer,andtimer.TheReleaserisresponsibleforlettingthecargoatthesamepointeachtime.TheMeasurerisresponsibleformeasuringthedistancethe car travels from the endof the table to thepoint it hits the floor (i.e. paper).Lastly,theTimerisresponsibleformeasuringthetimeittakesthecartotravelfromtheedgeofthetabletothefloor.RecordeachofthesemeasurementsforeachtrialintheTablebelow.

Diagram

DataTable

Trial#Distanced(m)

Timet3*(s)

Velocityv3x(m/s)

Run1

Run2

Run3

Run4

Run5

Average *ThisisthetimeforthecartotravelthroughtheairfromPosition2toPosition3justasthecarhitstheground.



Calculations-Showallsupportingcalculationsbelow.

1) UsingprincipleoftheConservationofEnergycalculatethetheoreticalvaluesforthePotentialEnergy(PE)andKineticEnergy(KE)atEachPositioninthetablebelow.

Position PotentialEnergy KineticEnergy TotalEnergy

1

NotApplicable

2

3 NotApplicable

a) Using the KE at Position 2, calculate the magnitude of the cars theoretical

velocityatPosition2.

b) UsingtheTotalEnergyfromPosition1or2,calculatethemagnitudeofthecarstheoreticalvelocityatPosition3.



2) Usingthedatayoucollected,calculatetheAverageDistance(dave)andtheAverage

Time(t3ave)ofyourtrialsandputthesevaluesintheirrespectivecolumnintheDataTable.Showonesamplecalculationofhowyoudeterminedthevelocity.

3) UsingtheresultsfromQuestion2above,calculatethex-componentofthevelocityofthecarasittravelsthroughtheair(i.e.fromPosition2toPosition3).Recallthatvelocityisdefinedasdisplacementovertime.

𝑣!! =𝑑!"#𝑡!!"#

4) Calculatethey-componentofthevelocityatPosition3.Sincethecarflyingthroughthe air it is being affected by gravity and we can no longer use the simplerelationshipweusedinQuestion3.RecallfromKinematicsthefollowingequation.

𝑣!! = 𝑣!! + 2𝑎𝑑

Were‘vi’and‘vf’istheinitialandfinaly-componentofvelocityrespectively,‘d’istheheightthecarfallstotheground(h2),and‘a’istheaccelerationduetogravity(g=9.81m/s2).

5) Drawandcalculatetheresultantvelocityjustbeforethecarhitstheground.



Questions

1) BaseduponyourmeasurementswhatisthevelocityatPosition2(Hint:youalreadycalculatedthis)?Explainwhyvelocityisthisvalue.

2) Baseduponyourresults,calculatetheKEatPosition2usingyourmeasureddata.IsitdifferentthanthetheoreticalvaluedeterminedinCalculation1,ifsobyhowmuch(expressfinalanswerasapercentage)?

3) Usingyourresults fromCalculation5,calculatethemeasuredKEatPosition3. Is itdifferentthanthetheoreticalvaluedeterminedinCalculation1b,ifsobyhowmuch(expressfinalanswerasapercentage)?

4) WhatdoyounoticeabouttheKineticEnergyatPositions1,2,and3?Explainwhythismakessense(Hint:isthereatrend?)

5) WasEnergyconservedbetweeneachposition(i.e.KE1+PE1=KE2+PE2=KE3+PE3)based upon your measured results? If not, are they reasonably close? Is there anoticeabletrend?Explain.



6) Assuming you started with 100% Energy at Position 1 (i.e. theoretical value), how

muchenergywasgainedorlostatPosition3(i.e.measuredvalue)?

7) HowmuchWork was done by gravity inmaking the car travel fromPosition 1 toPosition3?

ConcludingQuestions:

1) What are some possible sources of errors that could have led to a difference inenergybetweeneachpositionthatcouldaccountforthesedifferences?(Hint:thereareatleast3possiblesourcesthatcanleadtoerrors)

2) Whydidyouleavethe3–4inchesbetweentheendofthetrackandtheendofthetable?

3) How might one improve upon this experiment? Is there anything we could havedonedifferentlytoyieldbetterormoreaccurateresults?

4) Using theconservationofenergy, solve the followingproblem:A rock falls fromaheightof10metersaboveground.Whatisthevelocityoftherockjustbeforeithitstheground?Drawa neat and labeleddiagramand show supporting calculation aswellasformulasused.



ThisisacontinuationofourpreviousConservationofEnergyandEnergyTransferLab.Groupsof3:continuewithsamegroupmembersaspreviously.ObjectiveBytheendofthislabsession,youwillbeabletounderstandthePrincipleofConservationofEnergyaswellasbuilduponyourcurrentunderstandingofKinematics(motion).MaterialsRequired

• Bench/RetortStand• UtilityClamp• Track(4-5Sections)

• WeightScale• MetreStick/TapeMeasure• HotWheelsCar

• Tape• Protractor/Ruler• Bucket/Target

SetupWewillusethesamesetup,asbefore,exceptforthistimewewillbecreatingarampattheendoftrackasseenintheDiagramonthefollowingpage.Tip:youwilllikelyneedtotapethe track to the table atPosition 2 and create somewayof securelyholding the trackatPosition3…BeCreative!ProcedureInthislabyouwillbeperformingthecalculationsandtestingyourresults.Forthislabwewillignorefrictionallossesandairresistance…untiltheEND!Measurements

1) Usingthescaleprovidedmeasurethemassofyourcarinkilograms(kg).Recordthismeasurementonthediagram.Recall1kg=1000grams.

2) Markyourstartingpositiononthetrackusingasmallpieceoftape(thisistomakesure you release the car at exactly the same point each time. Next measure thisheight(h1)inmetersandrecorditonthediagram.

3) Nextmeasuretheheightofthetable(h2)inmetersandrecorditonthediagram.4) Nextmeasuretheheightoftheramp(h3)inmetersandrecorditonthediagram.5) Using trigonometry, find the launch angle (Θ) of your ramp and record this

measurementonthediagram.

YourName:_____________________Partner’sName:_____________________

_____________________Block:______



Diagram

RampDiagram

TABLE& Θ"="_____o"

BUCKET&

1&

2&3&

Car"Mass=_________"Kg"

4&

h1=_____"m"

d=_______"m"

h3=_____"m"Θ"

h2=_____"m"



1) UsingprincipleoftheConservationofEnergycalculatethetheoreticalvaluesforthePotentialEnergy(PE)andKineticEnergy(KE)atEachPositioninthetablebelow.

Position PotentialEnergy KineticEnergy TotalEnergy

1

NotApplicable

2

3

4 NotApplicable



2) Whatisthecar’stheoreticalvelocityatPosition3?

3) Calculatethetheoreticalx&y-componentofvelocityjustpriortothecarleavingthetrackatPosition3.Drawandlabelavectordiagramshowingthesecomponents.

4) UsingtheinformationfromQuestion3calculatethedistance(inthex-direction)thecarwill travel. (Hint:youwill firstneedtocalculatethetravel timeofthecar fromPosition3toPosition4)…recordthisdistanceontheDiagram.

5) Whatisthetheoreticalx&y-componentofvelocityatPosition4?Drawandlabelavectordiagramshowingthesecomponents.



VerificationBased upon your results inQuestion 5, get your teachers attention and theywill place abucket/targetatthiscalculateddistance…achanceforBonusMarks☺DidyourcarlandintheBucket/Bulls-Eye,YesorNo?________ifNo,wasclose!______cmIf your car made it into the bucket/bulls-eye, great work! If not and if you would like asecond chance to redeem yourself lets re-try the experiment, but this time taking intoconsiderationEnergyloss.MakealogicalguesstotheamountofenergythatislostduetoFriction,Sound,etc…EstimationoftheEnergyLoss=_____%Adjust your calculationsanddistance travelledby taking intoaccount this lossofenergy.Showanynecessaryworkandcalculationsbelow…getyourteacherwhenyou’rereadytotryagain!(Hint:youneedtocarefullythinkaboutwheretheenergylossisoccurring!)Questions

1) What are some reasons why your car may have not landed in the bucket/target?(Hint:thinkofpotentialsourcesoferrors).

2) Whatwouldbe theoptimal launchangle inorder toget thegreatest rangeoutoftheramp?Verifywithcomputations.

physics 12 unit: conservation of energy – lab #1

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