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Physics11
KinematicEquations3&4
LearningIntentions:
Ican:
ü Usethethirdkinematicequationtosolveproblemswherefinalvelocityisunknownü Usethefourthkinematicequationtosolveproblemswheretimeisunknownü Rewriteandcombinethethirdandfourthkinematicequationtosolveproblems
involvingdisplacement,velocity,acceleration,andtime
Equation#3:
Thethirdkinematicequationcomesfromcombiningthefirstandsecondequation.Thefirstequationissimplysubstitutedintothesecondinplaceof!":i.e.
# = %&' +)*+'
*
Thethirdequationshouldbeusedwhenever,, !., /, &2areknownbutthefinalvelocityisnotknown.
Physics11
Equation#4:
Thefourthequationisalsomadebycombiningthefirstandsecondequations.Thistime,however,thesecondequationissolvedfor/andissubstitutedintothefirstequation.i.e.
%3* = %&* + *+#
Thefourthequationcanbeusedwhenever!", !., 2, &,areknownbuttimeisnotknown.
Example:
Asprinterstartsfromrestandacceleratesuniformlyatarateof4.4456foratimeof6.757.Howfardoesthesprinterrun?
Physics11
OnyourOwn:
Acatiswalkingatanunknownvelocitywhenitspotsatoymouse608away.Thecatbeginstoaccelerateuniformlyatarateof3456.After6sthecatpouncesonthetoymouse.Whatwasthecat’sinitialvelocity?
Example:
Brendenisintodoingjumpsonhisdirtbike.Hedecideshewantstojumpovertopofaschoolbus.InorderforBrendentoclearthebus,hemusthitthejumpwithavelocityof3045 .Ifthejumpis18mawayfromthestartingpoint,whatmustBrenden’sconstantaccelerationbe?
Physics11
OnyourOwn:
Shawnajumpsoffoftheultra-highdivingboardintothepool.Iftheheightofthedivingboardis188whatvelocitydoesshehitthepoolat?(Assumeshestartsherfree-fallfromrest)
Example:
Anelectronisflyingaroundatavelocityof1.8×10> 45 .Asitnearsthenucleus,anattractiveforcecausesittoacceleratetowardsthenucleusatarateof2.4×10A 456.Iftheelectronhitsthenucleuswithavelocityof1.82×10> 45 ,howlongdoestheelectrontaketohitthenucleus?
Assignment:P.62#4-8