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