kinematics in one dimension

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Kinematics in One Dimension 1. Introduction 1. Different Types of Motion We'll look at: 2. Dimensionality in physics 3. One dimensional kinematics 4. Particle model 2. Displacement Vector 1. Displacement in 1-D 2. Distance Traveled 3. Speed and Velocity 1. ...with a direction 4. Change in velocity. 1. Acceleration 2. Acceleration, the math. 3. Slowing down 4. Acceleration in the negative 5. Summary of acceleration signage. 5. Kinematic equations 1. Equations of Motion (1-D) 6. Solving Problems 7. Plotting 8. Free Fall 1. Drop a wrench 2. How high was this? 3. Every point on a line has a tangent Introduction Motion: change in position or orientation with respect to time. Vectors have given us some basic ideas about how to describe the position of objects in the universe/ Now, we'll continue by extending those ideas to account for changes in that position. Of course the world would be awfully boring if the position of everything was constant. Different Types of Motion We'll look at: Linear motion involves the change in position of an object in one direction only. An example would be a train on a straight section of the track. The change in position is only in the horizontal direction. Projectile motion occurs when objects are launched in the gravitational field near the earths surface. They experience motion in both the horizontal and the vertical directions. Circular motion occurs in a few specific cases when an object travels in a perfect circle. Some special math can be used in these cases. Rotational motion implies that the body in question is rotating around an axis. The axis doesn't necessary need to pass through the object. ... or a combination of them . Dimensionality in physics PHY 20700 - 1 Dimensional Kinematics - J. Hedberg - 2021 Page 1 Updated on: 2021-2-2

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KinematicsinOneDimension1.Introduction

1.DifferentTypesofMotionWe'lllookat:2.Dimensionalityinphysics3.Onedimensionalkinematics4.Particlemodel

2.DisplacementVector1.Displacementin1-D2.DistanceTraveled

3.SpeedandVelocity1....withadirection

4.Changeinvelocity.1.Acceleration2.Acceleration,themath.3.Slowingdown4.Accelerationinthenegative5.Summaryofaccelerationsignage.

5.Kinematicequations1.EquationsofMotion(1-D)

6.SolvingProblems7.Plotting8.FreeFall

1.Dropawrench2.Howhighwasthis?3.Everypointonalinehasatangent

IntroductionMotion:changeinpositionororientationwithrespecttotime.

Vectorshavegivenussomebasicideasabouthowtodescribethepositionofobjectsintheuniverse/Now,we'llcontinuebyextendingthoseideastoaccountforchangesinthatposition.Ofcoursetheworldwouldbeawfullyboringifthepositionofeverythingwasconstant.

DifferentTypesofMotionWe'lllookat:Linearmotioninvolvesthechangeinpositionofanobjectinonedirectiononly.Anexamplewouldbeatrainonastraightsectionofthetrack.Thechangeinpositionisonlyinthehorizontaldirection.

Projectilemotionoccurswhenobjectsarelaunchedinthegravitationalfieldneartheearthssurface.Theyexperiencemotioninboththehorizontalandtheverticaldirections.

Circularmotionoccursinafewspecificcaseswhenanobjecttravelsinaperfectcircle.Somespecialmathcanbeusedinthesecases.

Rotationalmotionimpliesthatthebodyinquestionisrotatingaroundanaxis.Theaxisdoesn'tnecessaryneedtopassthroughtheobject.

...oracombinationofthem.

Dimensionalityinphysics

PHY 20700 - 1 Dimensional Kinematics - J. Hedberg - 2021

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Fig.1

Preludetoadvancedphysicsandengineering:Lateron,you'llhavetoexpandyournotionofdimensionsabit.Itwon'tsimplymeanstraightorcurvy,butwillinsteadbeusedtodescribethedegreesoffreedominasystem.Forexample,anorbitingbody,thoughitmovesinacirclewhichrequiresxandyvaluestodescribe,canalsobedescribedbyconsideringtheradiusandtheangleofrotationinstead.Thisisjustanothercoordinatesystem:polarcoordinates(usually: and ).Ifwedescribetheorbitingplanetinthissystem,andsay,it'sgoingaroundinaperfectcircle,thenthe valuedoesn'tchangeandthe valuebecometheonlydimensionofinterest.Let'sholdoffonthisapproachfornow,butwhenitcomesbacklateron,welcomeitwithopenarmsbecauseitallowsformuchmorepowerfulandsimpleanalysisofsystems.

OnedimensionalkinematicsForthecaseof1-dimensionalmotion,we'llonlyconsiderachangeofpositioninonedirection.

Itcouldbeanyofthethreecoordinateaxes.

Justadescriptionofthemotion,withoutattemptingtoanalyzethecause.Todescribemotionweneed:

1.CoordinateSystem(origin,orientation,scale)2.theobjectwhichismoving

1dkinematicswillbeourstartingpoint.Itisthemoststraightforwardandeasiestmathematicallytodealwithsinceonlyonepositionvariablewillbechangingwithrespecttotime.

ParticlemodelWe'llneedtouseanabstraction:

Allrealworldobjectstakeupspace.We'llassumethattheydon't.Inotherwords,thingslikecars,cats,andducksarejustpoint-likeparticles.

r θ

r θ

y

x

z

Fig.2Acoordinatesystem

0 20-20 40 60 80 100

+x (m)-x (m)

Fig.3A1-dcoordinatesystem

PHY 20700 - 1 Dimensional Kinematics - J. Hedberg - 2021

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Thisisourfirstrealabstraction.Again,sincewearetryingtopredicteverything,wewouldliketofigureouttherulesthatdescribehowanyobjectwouldmove.Takeatrainforexample.Ifweaskedaquestionlike"whendoestheCtrainenter59thstreetstation?",anatural

follow-upwouldbe"well,doyoumeanthefrontofthetrain,orthemiddleofthetrain,ortheendofthetrain?Eachoftheseanswersmightbedifferentbyafewseconds.

Howdowedealwiththis?Byconsideringthetraintobea'point',wecanneglecttheactuallengthofthetrainandfocusonwhat'smoreinteresting:howthetrainmoves.

Thegoalistofindtheunderlyingphysicsthatdescribesalltrains.Oncewedothat,thenwecanimproveourmodelbyincludinginformationaboutthelengthoftheindividualtrainweareinterestedin.

DisplacementVectorToquantifythemotion,we'llstartbydefiningthedisplacementvector.

Inthecaseofourwanderingbug,thiswouldbethedifferencebetweenthefinalpositionandtheinitialposition.

Thisfigureshowsthedisplacementvector .Thismightbedifferentthanthedistancetraveledbythebug(showninthedottedline).

NoteonNotation!isthesamethingas

isthesamethingas

Whendescribingmotions,weusuallyhaveaninitialpositionandafinalposition.Wecancallthese and respectively,whenwedoouralgebra.

Oranotherwayofwritingthesequantitiesistosayourinitialpositionis andourfinalpositionisjust .Thisisaslightlymoregeneralwayofwritingthings.

Displacementin1-D

0 20-20 40 60 80 100

+x (m)-x (m)

Here'sacarthatmovesfrom to creatingadisplacementvectorof:

Thecarthenreversesto .

0 20-20 40 60 80 100

+x (m)-x (m)

Theleadstoadisplacementvectorof .

Fig.4Theparticlemodel

x∆ x

Δx = x − x0

Δx

xf x

xi x0

xi xf

x0 x

x0 x

Δx = x − = 60m − 0m = 60mx0

x = −20

Δx = −80m

PHY 20700 - 1 Dimensional Kinematics - J. Hedberg - 2021

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Aboutnotation. ("deltax")referstothechangein .Thatis,differencebetweenafinalandinitialvalue:

Or,inwords,thefinalxpositionminustheoriginalxpositionisequaltothechangeinx.

DistanceTraveledTogetthedistancetraveled,wejustneettotakethemagnitudeofthedisplacementduringacertainmotion.

Thisequationwillonlybetrueifthedisplacementisalwaysinthesamedirection.Ifhowever,thedisplacementvectorweretochangedirectionduringatrip,thethedistancetraveledmightnotbeequaltothetotaldisplacement.Forexample,ifyouwalk100feetforward,thenturnaroundandwalk50backwards.Youdisplacementfromtheinitialtofinalpositionwillonlybe50feet,butyouwillhavewalkedatotalof150feet.

SpeedandVelocity

The'elapsedtime'isdeterminedinthesamewayasthedistance:

Again, isthestartingtime,and isthefinaltime.

TakingtheAtrainbetween59thand125thtakesabout8minutes.TheC,whichisalocal,takes12minutes(onagoodday).Findtheaveragespeedforbothofthesetrips.

...withadirectionCalculatingtheaveragespeeddidn'ttellusanythingaboutthedirectionoftravel.Forthis,we'llneedaveragevelocity.

Inmathematicalterms:

Δx x

Δx = x− x0

|Δx| = DistanceTraveled

AverageSpeed ≡Distanceinagiventime

Elapsedtime

Δt = t− .t0

t0 t

Example Problem#1:

AverageVelocity ≡DisplacementElapsedtime

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(SIunitsofaveragevelocityarem/s)Inone-dimension,velocitycaneitherbeinthepositiveornegativedirection.

ThinkingabouttheAtrain,it'sclearthatitsspeedandvelocitystayedessentiallyconstantbetween59thand125thideally).However,theCtrainhadtostartandstopat7stations.Toquantify,thisdifferenceinmotion,we'llneedtointroducetheconceptofinstantaneousvelocity.

Ifweimaginemakingmanymeasurementsofthevelocityoverthecourseofthetravel,byreducingthe weareconsidering,thenwecanbegintoseehowwecanmoreaccuratelyassessthemotionofthetrain.

Theconceptofinstantaneousvelocityinvolvesconsideringaninfinitesimallysmallsectionofthemotion:

Thiswillenableustotalkaboutthevelocityataparticle'sspecificpositionortimeratherthanforanentiretrip.

Ingeneral,thisiswhatwe'llmeanwhenwesay'velocity'or'speed'.

≡ =vx − x0t− t0

ΔxΔt

Δx

v = =limΔt→0

ΔxΔt

dx

dt

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Changeinvelocity.Naturally,inordertobeginmoving,anobjectmustchangeitsvelocity.

Here'sagraphofabicyclistridingataconstantvelocity.(Inthiscaseit's10m/s)

+x (m)100 20 30 40

0s 1s 2s

Now,here'sagraphofthesamebicyclistridingandchanginghisvelocityduringthemotion

+x (m)100 20 30 40

0s 1s 2s 3s

Intheuppermotiongraph,noticehowthelengthofthedisplacementvector isthesameateachintervalintime.Meaning,thatafter1secondhaspassed,thedisplacementis10m,afteranothersecondpasses,another10metersdisplacementhasoccurred,makingthetotaldisplacementequalto20m.Thisismotionataconstantvelocity.Thisalsoapparentinthelengthofthevelocityvectorsateachpoint.Theyarealwaysthesame.

Inthebottomgraph,thedisplacement,andvelocityvectors,changeeachtimetheyaremeasured.Thisisrepresentativeofmotionwithnon-constantvelocity.Thevelocityischangingastimemoveson.

AccelerationThischangeinvelocitywe'llcallacceleration,andwecandefineitinaverysimilarwaytoourdefinitionofvelocity:

Again,inthiscasewe'retalkingaboutaverageacceleration.

At ,theAtrainisatrestat59thstreet.5secondslater,it'stravelingnorthat19meterspersecond.Whatistheaverageaccelerationduringthistimeinterval?

Ifweconsideredthesameverysmallchangeintime,theinfinitesimalchange,thenwecouldtalkaboutinstantaneousacceleration

TheSIunitsofaccelerationaremeterspersecondpersecond,or .That'sprobablyalittlebitofaweirdunit,but,itmakessensetothinkaboutlikethis:

Acceleration,themath.Toquantifytotheaccelerationofamovingbody,saythiscar,we'llneedtoknowitsinitialandfinalvelocities

Thecarhasabuildinspeedometer,sowecanlookatthattogetthespeed,andifwedon'tchangedirection,thenthevelocitywillbealwayspointedinthesamedirection.

d→

= =av − v0t− t0

ΔvΔt

Example Problem#2:

t = 0

a = =limΔt→0

ΔvΔt

dv

dt

ms−2

or( )m

s

s

vel

s

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Forthiscaseofacarstartingfromrest,andthenincreasingvelocity,theaccelerationwillbeapositivequantity.

SlowingdownWhatifweaskaboutacarslowingdown.Now,our while .

Nowthemathlookslikethis:

Wenoticethattheaccelerationisnegative.

AccelerationinthenegativeWhatifthecarstartsacceleratinginthenegativedirection?

Now,eventhespeedisincreasing,thevelocityisgettingmorenegative.

Ifwedothemath,we'llseethattheaccelerationvectorpointsinthenegativedirection.

Summaryofaccelerationsignage.Whenthesignsofanobject’svelocityandaccelerationarethesame(insamedirection),theobjectisspeedingupWhenthesignsofanobject’svelocityandaccelerationareopposite(inoppositedirections),theobjectisslowingdownandspeeddecreases

+vx

t

+vx

t

+vx

t

+vx

t

Kinematicequations

Wecandoalotbyrearrangingtheseequations.

Putting from(1)into(2)willgiveus:

= = =av − v0t− t0

20mph − 0mph2s − 0s

20mph2s

= = +4.5ma9m/s2s

s−2

= +9m/sv0 v = 0

= = = − = −4.5m/av − v0t− t0

0m/s − 9m/s2s − 0s

9m/s2s

s2

1. = a = ⇒ v = + atav− v0

tv0

2. = ⇒ x− = t = ( + v)tvx− x0

t− t0x0 v

12

v0

v

3.x− = t+ ax0 v012

t2

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or,solving(1)for ,theninsertingthatinto(2)willgiveus:

1.2.3.4.

Herewehaveanequationforvelocitywhichischangingduetoanacceleration, .

Ittellsushowfastsomethingwillbegoing(andthedirection)ifhasbeenacceleratedforatime, .

Itcandetermineanobject’svelocityatanytimetwhenweknowitsinitialvelocityanditsaccelerationDoesnotrequireorgiveanyinformationaboutpositionEx:“Howfastwasthecargoingafter10secondswhileacceleratingfromrestat10m/s ”Ex:“Howlongdidittaketoreach20milesperhour”

Thisequationwilltellusthepositionofanobjectbasedontheinitialandfinalvelocities,andthetimeelapsed.

Itdoesnotrequireknowing,norwillitgiveyou,theaccelerationoftheobject.

Ex:Howfardidtheduckwalkifittook10secondstoreach50milesperhourunderconstantacceleration.

Givespositionattimetintermsofinitialvelocityandacceleration

Doesn’trequireorgivefinalvelocity.Ex:“Howfarupdidtherocketgo?”

Givesvelocityattimetintermsofaccelerationandposition

Doesnotrequireorgiveanyinformationaboutthetime.Ex:“Howfastwaspennygoingwhenitreachedthebottomofthewell?”

EquationsofMotion(1-D)Thingstobeawareof:

1.Theyareonlyforsituationswheretheaccelerationisconstant.2.Thewaywehavewrittenthemisreallyjustfor1-Dmotion.

t

4. = + 2a(x− )v2 v20 x0

v = + atv0x = t = ( + v)tv 1

2v0

x = + t+ ax0 v012

t2

= + 2axv2 v20

v = + atv0

a

t

2

x = t =v(v+ )tv0

2

x = + t+x0 v0at2

2

= + 2axv2 v20

PHY 20700 - 1 Dimensional Kinematics - J. Hedberg - 2021

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Equation MissingVariable Goodforfinding

, ,

, ,

, ,

, ,

SolvingProblems1.Diagram:drawapicture2.Characters:Considertheproblemastory.Whoarethecharacters?3.Find:clearlylistsymbolicallywhatwe'relookingfor.4.Solve:statethebasicideabehindsolution,inafewwords(physicalprinciplesused,etc.)5.Assess:doesanswermakesense?

Ataxiissittingataredlight.Thelightturnsgreenandthetaxiacceleratesat2.5m/s for3seconds.Howfardoesittravelduringthistime?

Aparticleisatrest.Whataccelerationvalueshouldwegiveitsothatitwillbe2metersawayfromitsstartingpositionafter0.4seconds?

Asubwaytrainacceleratesstartingatx=200muniformlyuntilitreachesx=350m,atauniformaccelerationvalueof0.5m/s .

a.Ifithadaninitialvelocityof0m/s,whatwillthedurationofthisaccelerationbe?b.Ifithadaninitialvelocityof8m/s,whatwillthedurationofthisaccelerationbe?

If ,find and .Also,findthetimewhenthevelocityiszero.

TraianVuia,aRomanianInventor,wantedtoreach17m/sinordertotakeoffinhisflyingmachine.Hisplanecouldaccelerateat2m/s .Theonlyrunwayhehadaccesstowas80meterslong.Willhereachthenecessaryspeed?

v = + atv0 x a t v

x = (v+ )tv02

a x t v

x = + t+x0 v0at2

2v x a t

= +2axv2 v20 t a x v

Example Problem#3:

2

Example Problem#4:

Example Problem#5:

2

Example Problem#6:

x(t) = 4 − 27t+ t3 v(t) a(t)

Example Problem#7:

2

PHY 20700 - 1 Dimensional Kinematics - J. Hedberg - 2021

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Plotting

+x (ft)0 10 20 30 40 50

1s0s 2s 3s 4s 5s 6s 7s 8s 9s

Let'slookatthemotionofahoneybadger.

Aftereachsecond,wenotewherethehoneybadgerisalongthexaxis.

t[s] x[ft]

0 0.00

1 5.00

2 10.0

3 15.0

4 17.5

5 20.0

6 22.5

7 25.0

8 35.0

9 50.0

dist

ance

[ft]

0

10

20

30

40

50

time [s]1 2 3 4 5 6 7 8 9 10

Derivekinematicsusingcalculus.

Wecanderivenearlyallofkinematics(forcasseswithconstantacceleration)byconsideringtherelationshipsbetweenderivativesandintegrals.Let'sbeginwiththedefinitionofacceleration:

Ifwemakethe and infinitesimallysmall, and ,thenwecanrewritethisas:

a =Δv

Δt

Δv Δv dv dt

a = ⇒ dv = a dtdv

dt

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Now,wecantaketheindefiniteintegralofbothsides:

Since isassumedtobeconstant,wecanremovefromtheintegrand.Performingtheindefiniteintegrals:

where istheconstantofintegration.Todeterminetheconstant ,considertheequationwhen .Thisisthe'initialcondition',thusthevelocityatthispointwillbetheinitialvelocity: .Wethereforeobtain:

byconsideringjustthedefinitionofaccelerationandtheconceptofintegration.

Wecanlikewiseconsiderthedefinitionofinstantaneousvelocity:

Asimilaroperationleadsto:

Now,wecannotremove fromthisintegrandsinceitisnotaconstantvalue.However,wejustfiguredoutarelationbetweenvelocityandtimeabove,so:

Inthiscase, and arebothconstants.Sotheindefiniteintegralcanbesolved:

Again,wehaveaconstantofintegrationtosolvefor: .Let'sagainconsider ,i.e.theinitialcondition.When ,theobjectwillbelocatedattheinitial position, .Thus .Finally,wehaveanequationfor asafunctionoftimegivenalltheinitialconditionsofpositionandvelocity:

Thisisourfundamentalquadraticequationthatdescribesthemotionofaparticleundergoingtranslationwithconstantacceleration.

v(t)

t0

x(t)

t0

x(t)

t0

velocityasafunctionoftime: Accelerationisconstant

positionasafunctionoftime .(vel.constant,accel=0)

positionasafunctionoftime

∫ dv = ∫ a dt

a

v = at+ C1

C1 C t = 0v0

v = + atv0

v =dx

dt

∫ dx = ∫ v dt

v

∫ dx = ∫ ( + at) dtv0

v0 a

x = t+ a +v012

t2 C2

C2 t = 0 t = 0x x0 =C2 x0 x

x = + t+ ax0 v012

t2

v = + atv0 x = vtx = t+v0

at2

2

v(t) x(t)

Example Problem#8:

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Aturtleandarabbitaretohavearace.Theturtle’saveragespeedis0.9m/s.Therabbit’saveragespeedis9m/s.Thedistancefromthestartinglinetothefinishlineis1500m.Therabbitdecidestolettheturtlerunbeforehestartsrunningtogivetheturtleaheadstart.What,approximately,isthemaximumtimetherabbitcanwaitbeforestartingtorunandstillwintherace?

Acarandamotorcycleareat at .Thecarmovesataconstantvelocity .Themotorcyclestartsatrestandaccelerateswithconstantaccelerationa.

a.Findthe wheretheymeet.b.Findtheposition wheretheymeet.c.Findthevelocityofthemotorcyclewhentheymeet.

Thisproblemisaskingustodescribethekinematicsofthesituationinthemostgeneraltermspossible.Therearenonumbersgiven,sowemustdoeverythingusingsymbolicalgebra.First,let'smakesureweunderstandthesetup.Therearetwovehicles:acarandamotorcycle.Theycanbeconsideredparticlesmeaningtheyarepointlike.Theactionstartsatt=0.Atthistime,bothvehiclesarelocatedattheorigin.Themotorcycleisstationary,butthecarhasavelocity, .(* isjustasymbolthatcouldbeanumber,like10m/sor34.3mph.Butweleaveitasasymbolsothatwecansolvethisprobleminageneralway,applicabletoanycar!)Nowthecarwillmovefartherthanthemotorcycleatfirst.However,themotorcyclewillcatchupandovertakethecarbecauseitisaccelerating.

a)Findoutwhen,i.e.atwhattime,theyareatthesameposition.So,weneedfunctionsthattelluswhereeachvehicleislocatedatagiventime.Wecanstartwiththebasickinematicequationofmotion:

Forthecar,sincethereisnoacceleration, ,and ,thisequationsimplifiesto:

Forthemotorcycle,ithasnointitialvelocity, ,butitdoeshasanacceleration .Italsostartsfromtheorigin:

Thequestionaskwhentheobjectsmeet?Thatis,whenarethexvaluesthesame.So,wecanjustsetthetwoequationsequaltoeachother.

andsolvethisfor .

.Nowwehaveanequationfor thatwecanusegivenanyaccelerationandinitialvelocity.

b)Wheredoesthisoccur?Wecanusethetimeexpressioninoneofthepreviouspositionequations.

Itshouldalsobethesameifweputinthetimeinthemotorcycle'spositionequation:

c)Whatisthespeedofthemotorcycle?Wefirstneedtofindanequationforspeedofthemotorcycles.Let'stherelationshipbetween

Example Problem#9:

= 0x0 t = 0 v0

t

x

v0 v0

x = + t+ ax0 v012

t2

a = 0 = 0x0

= txcar v0

= 0v0 a

= axmoto12

t2

=xcar xmoto

t = av012

t2

t

t =2v0

a

t

= = 2xcar v02v0

a

v20

a

= a = a = 2xmoto12

t212

( )2v0

a

2 v20

a

PHY 20700 - 1 Dimensional Kinematics - J. Hedberg - 2021

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positionandvelocity:

So,whentimeis ,thespeedofthemotorcyclewillbe:

Noticehowtheaccelerationtermisgone.Thespeedofthemotorcyclewhenthetwoobjectmeetisindependentofitsacceleration.That'saninterestingbitofinformationthatwouldhavebeenlostifwedidthisproblemusingnumbersinsteadofletters.

x

t(s)

x

t(s)

carmeeting time

motorcycle

Thisplotshowsgraphicallythesituation.Wecancomparetheslopesthattheintersectionandseethattheslopeofthemotorcycleisroughlytwicethatofthecar.

FreeFallAfreelyfallingobjectisanyobjectmovingfreelyundertheinfluenceofgravityalone.

Objectcouldbe:

1.Dropped=releasedfromrest2.Throwndownward3.Thrownupward

Itdoesnotdependupontheinitialmotionoftheobject.

1.Theaccelerationofanobjectinfreefallisdirecteddownward(negativedirection),regardlessoftheinitialmotion.

2.Themagnitudeoffreefallaccelerationis .

3.Wecanneglectairresistance.4.We'llchooseouryaxistobepositiveupward.5.ConsidermotionnearEarth’ssurfacefornow.

v = = atdx

dt

t = 2v0a

v = at = a ( ) = 22v0

av0

9.8m/ = gs2

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Kinematicequationinthecaseoffreefall:

1.2.3.4.

Theyarethesame.Wejustreplaced and .

Anobjectisthrownupwardat20m/s:

a.Howlongwillittaketoreachthetopb.Howhighisthetop?c.Howlongtoreachthebottom?d.Howfastwillitbegoingwhenitreachesthebottom?

Ifanobjectisthrownupwardfromaheight withaspeed ,whenwillithittheground?

DropawrenchAworkerdropsawrenchdowntheelevatorshaftofatallbuilding.

a.Whereisthewrench1.5secondslater?b.Howfastisthewrenchfallingatthattime?

Arockisthrownupwardwithavelocityof49m/sfromapoint15mabovetheground.

a.Whendoestherockreachitsmaximumheight?b.Whatisthemaximumheightreached?c.Whendoestherockhittheground?

Howhighwasthis?

Drawposition,velocity,andaccelerationgraphsasafunctionsoftime,foranobjectthatisletgofromrestoffthesideofacliff.

v = − gtv0y = t = ( + v)tv 1

2v0

y = + t− gy0 v012

t2

= − 2gyv2 v20

x → y a → −g

Example Problem#10:

Example Problem#11:

y0 v0

Example Problem#12:

Example Problem#13:

Example Problem#14:

PHY 20700 - 1 Dimensional Kinematics - J. Hedberg - 2021

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