Kinetic Energy - Definition, Units, Equation, Examples ... - Byju's

Kinetic energy is the measure of the work that an object does by virtue of its motion. Simple activities like walking, jumping, throwing, ... CheckoutJEEMAINS2022QuestionPaperAnalysis: CheckoutJEEMAINS2022QuestionPaperAnalysis: × DownloadNow PhysicsEnergyKineticEnergy KineticEnergy Kineticenergyisthemeasureoftheworkthatanobjectdoesbyvirtueofitsmotion.Simpleactivitieslikewalking,jumping,throwing,andfallinginvolvekineticenergy.Inthisarticle,letusfamiliariseourselveswiththeconceptofkineticenergy. TableofContents WhatisKineticEnergy? KineticEnergyUnits KineticEnergyExamples KineticEnergyTransformation KineticEnergyFormula KineticEnergyEquationDerivation KineticEnergy:ascalaroravector? KineticEnergyCalculation KineticEnergyTypes RadiantEnergy ThermalEnergy SoundEnergy ElectricalEnergy MechanicalEnergy OverviewofKineticEnergy DifferenceBetweenKineticandPotentialEnergy FrequentlyAskedQuestions–FAQs WhatisKineticEnergy? Toaccelerateanobject,wehavetoapplyforce.Toapplyforce,weneedtodowork.Whenworkisdoneonanobject,energyistransferred,andtheobjectmoveswithanewconstantspeed.Wecalltheenergythatistransferredkineticenergy,anditdependsonthemassandspeedachieved. ThekineticenergydefinitioninPhysicsisgivenas: Kineticenergyofanobjectisthemeasureoftheworkanobjectcandobyvirtueofitsmotion. Kineticenergyisascalarquantity,anditisentirelydescribedbymagnitudealone. UnitsofKineticEnergy TheSIunitofkineticenergyisJoulewhichisequalto1kg.m2.s-2. TheCGSunitofkineticenergyiserg. KineticEnergyExamples Atrucktravellingdowntheroadhasmorekineticenergythanacartravellingatthesamespeedbecausethetruck’smassismuchmorethanthecar’s. Ariverflowingatacertainspeedcompriseskineticenergyaswaterhasacertainvelocityandmass. Thekineticenergyofanasteroidfallingtowardsearthisverylarge. Thekineticenergyoftheaeroplaneismoreduringtheflightduetoitslargemassandspeedyvelocity. KineticEnergyTransformation Kineticenergyistransferredbetweenobjectsandcanbetransformedintootherformsofenergy.Yo-Yoisagreatexampletodescribethetransformationofkineticenergy.Whilebeginningtoplaywithit,onestartsbylettingitrestinhand;atthispoint,alltheenergyisstoredintheballintheformofpotentialenergy.Oncethepersondropstheyo-yo,thestoredenergyistransformedintokineticenergy,theenergyofmovement.Oncetheballreachesthebottomoftheyo-yo,alltheenergyisconvertedtokineticenergy. SimilarReading: Scalarquantity Potentialenergy TheFormulaforKineticEnergy Thekineticenergyequationisgivenas: \(\begin{array}{l}KE=\frac{1}{2}mv^{2}\end{array}\) WhereKEisthekineticenergy,misthebody’smass,andvisthebody’svelocity. DerivingKineticEnergyEquation Kineticenergyequationcanbeobtainedbythebasicprocessofcomputingthework(W)thatisdonebyaforce(F).Ifthebodyofmassmwaspushedforadistanceofdonasurfacebyapplyingaforcethat’sparalleltoit,thentheworkdonewouldbe: \(\begin{array}{l}W=F.d=m.a.d\end{array}\) Theaccelerationinthisequationcanbesubstitutedbytheinitial(vi)andfinal(vf)velocityandthedistance.Thiswegetfromthekinematicequationsofmotion. \(\begin{array}{l}W=m.a.d\\\\=m.d.\frac{v_{f}^{2}-v_{i}^{2}}{2d}\\\\=m.\frac{v_{f}^{2}-v_{i}^{2}}{2d}\\\\=\frac{1}{2}.m.v_{f}^{2}-\frac{1}{2}.m.v_{i}^{2}\end{array}\) Simplifyingtheequationfurther,weget \(\begin{array}{l}K.E=\frac{1}{2}mv^{2}\end{array}\) Alternately,onecansaythatthetotalworkthatisdoneonasystemisequivalenttothechangeinkineticenergy.Thisstatementisequatedasfollows: \(\begin{array}{l}W_{net}=\DeltaK\end{array}\) Thisequationisknownasthework-energytheoremandhaslargeapplicationseveniftheforcesappliedvaryinmagnitudeanddirection. ReadMore:DerivationOfKineticEnergy IsKineticEnergyaVectororaScalarQuantity? Intheexpression,weseethatvelocity(v)issquared.Weknowthatthesquareofavectorquantityisascalar,andwealsoknowthatmassisascalarquantity.Therefore,kineticenergyisascalarquantity. KineticEnergyCalculation 1.Calculatethekineticenergyofa200kgobjectthatismovingataspeedof15m/s. Solution: Thekineticenergyofthebodycanbecalculatedusingthefollowingequation: \(\begin{array}{l}KE=\frac{1}{2}mv^2\end{array}\) Substitutingthevaluesintheaboveequation,weget \(\begin{array}{l}KE=\frac{1}{2}(200\,kg)(15\,m/s)^2\end{array}\) \(\begin{array}{l}KE=45000\,J\,or\,45\,KJ\end{array}\) 2.Calculatethemassoftheobjectmovingataspeedof40m/sandhavingakineticenergyof1500J. Solution: Rearrangingthekineticenergyequation,weget \(\begin{array}{l}m=\frac{2KE}{v^2}\end{array}\) Substitutingthevaluesintheaboveequation,weget, \(\begin{array}{l}m=\frac{2\times1500}{40^2}=1.87\,kg\end{array}\) TypesofKineticEnergy Therearefivetypesofkineticenergy:radiant,thermal,sound,electricalandmechanical.Letuslookatsomeofthekineticenergyexamplesandlearnmoreaboutthedifferenttypesofkineticenergy. Radiantenergy Radiantenergyisatypeofkineticenergythatisalwaysinmotiontravellingthroughmediumorspace.Examplesofradiantenergyare: Ultravioletlight Gammarays Thermalenergy Thermalenergy,knownasheatenergy,isgeneratedduetothemotionofatomswhentheycollidewitheachother.Examplesofthermalenergyare: Hotsprings Heatedswimmingpools Soundenergy Thevibrationofanobjectproducessoundenergy.Soundenergytravelsthroughthemediumbutcannottravelinavacuumastherearenoparticlestoactasamedium.Examplesofsoundenergyare: Tuningfork Beatingdrums Electricalenergy Electricalenergyisobtainedfromthefreeelectronsthatareofpositiveandnegativecharge.Examplesofelectricalenergyare: Lightning Batterieswheninuse Mechanicalenergy Thesumofkineticenergyandpotentialenergyisknownasmechanicalenergy,whichcanneitherbecreatednorbedestroyedbutconvertedfromoneformtoanother.Examplesofmechanicalenergyare: Orbitingofsatellitesaroundtheearth Amovingcar Readmore:LawofConservationofEnergy OverviewofKineticEnergy KineticEnergyDefinition Kineticenergyisthemeasureoftheworkanobjectcandobythevirtueofitsmotion. KineticEnergyEquation \(\begin{array}{l}KE=\frac{1}{2}mv^{2}\end{array}\) KineticEnergyUnits TheSIunitofkineticenergyisJouleswhichisequaltokg-m2s-2 KineticEnergyExamples Ariverflowingatacertainspeed KineticEnergyTypes Radiantenergy,Thermalenergy,Soundenergy,ElectricalenergyandMechanicalenergy. DifferenceBetweenKineticEnergyandPotentialEnergy Kineticenergy Potentialenergy Kineticenergyisaformofenergypossessedbyanobjectduetoitsmotion. Potentialenergyistheformofenergypossessedbyanobjectduetoitspositionorstate. Formulausedis \(\begin{array}{l}KE=\frac{1}{2}mv^{2}\end{array}\) Theformulausedismgh Vibrationalenergyisanexampleofkineticenergy Gravitationalpotentialenergyisanexampleofpotentialenergy ReadMore:DifferencebetweenKineticandPotentialEnergy Formoreinformationonkineticenergyandpotentialenergy,watchthebelowvideos: RelatedLinks WhatIsEnergy? Whatis EnergyConversion? RelationBetweenKineticEnergyandMomentum FrequentlyAskedQuestions–FAQsWhatisthedefinitionofkineticenergy?Thekineticenergyisthemeasureoftheworkanobjectcandobyvirtueofitsmotion.Canthekineticenergybenegative?Thekineticenergycannotbenegativebecausethesquareofthespeedgivesanon-negativenumber,andthemasscannotbenegative.Whenisthekineticenergymaximum?Thekineticenergyismaximumwhenthepotentialenergyisminimum,andthisoccurswhenthevelocityismaximumandthemassisattheequilibriumposition.Whathappenstothekineticenergywhenthespeeddecreases?Whenthespeeddecreases,thekineticenergywillbetransformedintopotentialenergy,thermalenergyorotherformsofenergy.Howisthekineticenergydifferentfromthepotentialenergy?Theenergypossessedbythebodybyvirtueofitspositionisknownaspotentialenergy.Theenergypossessedbythebodybyvirtueofitsmotionisknownaskineticenergy. StaytunedtoBYJU’SandFallinLovewithLearning! TestyourknowledgeonKineticenergy Q5 PutyourunderstandingofthisconcepttotestbyansweringafewMCQs.Click‘StartQuiz’tobegin! 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