WhatYou’llLearn•Youwillexaminevibrationalmotionandlearnhowitrelatestowaves.•Youwilldeterminehowwavestransferenergy.•Youwilldescribewavebehavioranddiscussitspracticalsignificance.WhyIt’sImportantKnowledgeofthebehaviorofvibrationsandwavesisessentialtotheunderstandingofresonanceandhowsafebuildingsandbridgesarebuilt,aswellashowcommunicationsthroughradioandtelevisionareachieved.“GallopingGertie”Shortlyafteritwasopenedtotraffic,theTacomaNarrowsBridgenearTacoma,Washington,begantovibratewheneverthewindblew(seeinset).Oneday,theoscillationsbecamesolargethatthebridgebrokeapartandcollapsedintothewaterbelow.ThinkAboutThis�Howcouldalightwindcausethebridgeintheinsetphototovibratewithsuchlargewavesthatiteventuallycollapsed?374physicspp.comMichaelT.Sedam/CORBIS,(inset)CORBISHowdowavesbehaveinacoiledspring?QuestionHowdopulsesthataresentdownacoiledspringbehavewhentheotherendofthespringisstationary?Procedure1.Stretchoutacoiledspiralspring,butdonotoverstretchit.Onepersonshouldholdoneendstill,whiletheotherpersongeneratesasidewayspulseinthespring.Observethepulsewhileittravelsalongthespringandwhenithitstheheldend.Recordyourobservations.2.Repeatstep1withalargerpulse.Recordyourobservations.3.Generateadifferentpulsebycompressingthespringatoneendandlettinggo.Recordyourobservations.4.Generateathirdtypeofpulsebytwistingoneendofthespringandthenreleasingit.Recordyourobservations.AnalysisWhathappenstothepulsesastheytravelthroughthespring?Whathappensastheyhittheendofthespring?Howdidthepulseinstep1comparetothatgeneratedinstep2?CriticalThinkingWhataresomepropertiesthatseemtocontrolhowapulsemovesthroughthespring?14.1PeriodicMotion�Objectives•Describetheforceinanelasticspring.•Determinetheenergystoredinanelasticspring.•Comparesimpleharmonicmotionandthemotionofapendulum.�VocabularyperiodicmotionsimpleharmonicmotionperiodamplitudeHooke’slawpendulumresonanceYou’veprobablyseenaclockpendulumswingbackandforth.Youwouldhavenoticedthateveryswingfollowedthesamepath,andeachtripbackandforthtookthe...
