【经典美国高中物理教材】Physics Principles and Problems(Chapter 14 Vibrations and Waves)

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1、374-380CH14-S1-8458133/30/045:30AMPage374WhatYou’llLearn•Youwillexaminevibrationalmotionandlearnhowitrelatestowaves.•Youwilldeterminehowwavestransferenergy.•Youwilldescribewavebehavioranddiscussitspracticalsignificance.WhyIt’sImportantKnowledgeofthebehaviorofvibration

2、sandwavesisessentialtotheunderstandingofresonanceandhowsafebuildingsandbridgesarebuilt,aswellashowcommunicationsthroughradioandtelevisionareachieved.“GallopingGertie”Shortlyafteritwasopenedtotraffic,theTacomaNarrowsBridgenearTacoma,Washington,begantovibratewheneverthe

3、windblew(seeinset).Oneday,theoscillationsbecamesolargethatthebridgebrokeapartandcollapsedintothewaterbelow.ThinkAboutThis
Howcouldalightwindcausethebridgeintheinsetphototovibratewithsuchlargewavesthatiteventuallycollapsed?physicspp.com374MichaelT.Sedam/CORBIS,(inset)C

4、ORBIS374-380CH14-S1-8458136/4/048:53AMPage375Howdowavesbehaveinacoiledspring?QuestionHowdopulsesthataresentdownacoiledspringbehavewhentheotherendofthespringisstationary?ProcedureAnalysis1.Stretchoutacoiledspiralspring,butdonotWhathappenstothepulsesastheytraveloverstre

5、tchit.Onepersonshouldholdonethroughthespring?Whathappensastheyendstill,whiletheotherpersongeneratesahittheendofthespring?Howdidthepulseinsidewayspulseinthespring.Observethestep1comparetothatgeneratedinstep2?pulsewhileittravelsalongthespringandCriticalThinkingWhatareso

6、mepropertieswhenithitstheheldend.Recordyourthatseemtocontrolhowapulsemovesthroughobservations.thespring?2.Repeatstep1withalargerpulse.Recordyourobservations.3.Generateadifferentpulsebycompressingthespringatoneendandlettinggo.Recordyourobservations.4.Generateathirdtype

7、ofpulsebytwistingoneendofthespringandthenreleasingit.Recordyourobservations.14.1PeriodicMotionou’veprobablyseenaclockpendulumswingbackandforth.You
ObjectivesYwouldhavenoticedthateveryswingfollowedthesamepath,and•Describetheforceinaneachtripbackandforthtookthesameamoun

8、toftime.Thisactionisanelasticspring.exampleofvibrationalmotion.Otherexamplesincludeametalblockbob-•Determinetheenergybingupa