英语阅读给个标准答案Ifamotherpusheshersm-查字典问答网
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  英语阅读给个标准答案Ifamotherpusheshersmallsoninaswing,givingonlyalightforceeachtimehereturns,eventuallyhewillbeswingingquitehigh.Thechildcandothisforhimselfbyusinghislegstoincreasethemotion,butboththe

  英语阅读给个标准答案

  Ifamotherpusheshersmallsoninaswing,givingonlyalightforceeachtimehereturns,eventuallyhewillbeswingingquitehigh.Thechildcandothisforhimselfbyusinghislegstoincreasethemotion,butboththemother'spushandthechild'slegmovementsmustoccuratthepropermoment,ortheextentoftheswingwillnotincrease.Inphysics,increasingtheswingisincreasingtheamplitude;thelengthoftheropeontheswingdeterminesitsnaturaloscillationperiod.Thisabilityofanobjecttomoveperiodicallyortovibratewhenstimulatedbyaforceoperatinginitsnaturalperiodiscalledresonance.

  Resonanceisobservedmanytimeswithoutconsciouslythinkingaboutit;forexample,onemayfindanannoyingvibrationorshimmyinanautomobile,causedbyalooseenginemountvibratingwithincreasingamplitudebecauseofanout-of-roundtire.Thebulgeonthetireslapsthepavementwitheachrevolution;atthenaturalresonancepoint~oftheenginemount,itwillbegintovibrate.Suchvibrationscanresultinconsiderabledamageifallowedtopersist.Antherdestructiveexampleofresonanceistheshatteringofacrystalgobletbytheproductionofamusicaltoneatthenaturalresonantpointofthegoblet.Theenergyofthesoundwavescausesvibrationintheglass;asitsamplitudeincreases,themotionintheglassexceedstheelasticityofthegoblet,anditshatters.

  Aninstrumentcalledatachometermakesuseoftheprincipleofresonance.Itconsistsofmanytinybars,looselyfastenedtogetherandarrangedsothateachbarcanslideindependentlyoftheothers.Movementofthebarscauseschangesinadial.Whenplacednexttoarotatingmotororengine,thetachometerpicksupslightvibrationswhicharetransferredtotheresonantbars.Thesebarsbegintomove,andtheresultingdialmaybereadtofindtherevolutionsperminuteofthemotorveryquickly.

  74.Anobject,ifmovingrhythmicallywhenstimulatedinanaturalperiod,issaidto

  A.vibrate.B.resonate.C.swing.D.oscillate.

  75.Thedistanceaswingmovesfromitsrestingpositioniscalledits

  A.revolution.B.movement.C.frequency.D.amplitude.

  76.Atachometerisaninstrumentthatusesresonancetodetermine

  A.thespeedofamotorinrevol

1回答
2020-06-22 14:57
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李康宁

  B,D,D,B,B第一问题请看这句话:Thisabilityofanobjecttomoveperiodicallyortovibratewhenstimulatedbyaforceoperatinginitsnaturalperiodiscalledresonance.第二个问题:基本常识,肯定是振幅...

2020-06-22 15:01:34

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