mechanic waves

《mechanic waves》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、WaveThedifferentMechanicalwaveswaterwavessoundwavesseismicwaves(地震波)Thesewaveshavecertaincentralfeatures:TheyaregovernedbyNewton’slaws,andtheycanexistonlywithinamaterialmedium,suchaswater,air,androck.1.TransverseWaves(横波，S波)Thedirectionofoscillationofmediumelementsisperpendicular(垂

2、直)tothedirectionoftravelofthewave.TwotypeofMechanicalwaves2.LongitudinalWaves(纵波，P波)Thedirectionofoscillationofmediumelementsisparallel(平行)tothedirectionofthewave’stravel,themotionissaidtobelongitudinal,andthewaveissaidtobealongitudinalwave.Bothatransversewaveandalongitudinalwavear

3、esaidtobetravelingwavesbecausetheybothtravelfromonepointtoanother,asfromoneendofthestringtotheotherend.sparseanddenseTheTides1Themoon’sgravityactsontheearthThemoon’sgravityisn’tuniformTheearth’soceansarepulledoutofroundT=24hour48minTheTides2TherearetwotidalbulgesintheoceansAstheear

4、throtates,thesebulgesshiftAlmost2highand2lowtidesperdayStrongesttidesnearequatorWeakesttidesnearpolesTheSun’sInfluenceSun’sgravityaffectstidesStrongesttideswhenmoonandsunarealignedWeakesttideswhenmoonandsunareatrightanglesWaterWavesSloshinginvolvesdeepwaterwaves:thewholeliquidmoves

5、backandforthSurfacewavesonlyaffecttheliquid’stopWater’sMotionSurfacewatercirclesasthewavepassesCirclingisstrongestatsurfaceMotionisweakabout1/2wavelengthdeepWaterinaWaveOnlythewavetravels,thewatercirclesCrestsareformedfromlocalwaterQuestion:Youarefloatingmotionlessinaninnertube.You

6、arenearabeachbutfarenoughfromtheshorethatwavesaren'tbreakingontopofyou.YouwilldrifttowardshoreatthespeedofthewavesdriftgraduallytowardshorecircleaswavespassbutnotprogresstowardshoreWavelengthThelongerthewavelengthofasurfacewave,thefasterittravelsthedeeperwatermovesasitpassesthemore

7、energyitcontainsforagivenamplitudeTsunamis（海啸）areverylongwavelength,verydeep,veryhighenergywavesThepoweroftsunamisTsunamisattackJapan11March,2011How?BreakingWavesSurfacewavesslowdowninshallowwaterWavesbunchasthewatergetsshallowerWavesgettallerasthewatergetsshallowerWavesbreakwhen

8、watercan’tformcrestGradual