2023年全國碩士研究生考試考研英語一試題真題（含答案詳解+作文范文）_第1頁
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1、英文原文英文原文BrakesystemsWeallknowthatpushingdownonthebrakepedalslowsacartoastop.ButhowdoesthishappenHowdoesyourcartransmitthefcefromyourlegtoitswheelsHowdoesitmultiplythefcesothatitisenoughtostopsomethingasbigasacarWhenyoude

2、pressyourbrakepedalyourcartransmitsthefcefromyourfoottoitsbrakesthroughafluid.Sincetheactualbrakesrequireamuchgreaterfcethanyoucouldapplywithyourlegyourcarmustalsomultiplythefceofyourfoot.Itdoesthisintwoways:?Mechanicala

3、dvantage(leverage)?HydraulicfcemultiplicationThebrakestransmitthefcetothetiresusingfrictionthetirestransmitthatfcetotheroadusingfrictionalso.Befewebeginourdiscussiononthecomponentsofthebrakesystemwellcoverthesethreeprinc

4、iples:?Leverage?Hydraulics?FrictionLeverageHydraulicsInthefigurebelowafceFisbeingappliedtotheleftendofthelever.Theleftendoftheleveristwiceaslong(2X)astherightend(X).Therefeontherightendoftheleverafceof2Fisavailablebutita

5、ctsthroughhalfofthedistance(Y)thattheleftendmoves(2Y).Changingtherelativelengthsoftheleftrightendsoftheleverchangesthemultipliers.Thebasicideabehindanyhydraulicsystemisverysimple:Fceappliedatonepointistransmittedtoanothe

6、rpointusinganincompressiblefluidalmostalwaysanoilofsomest.Mostbrakesystemsalsomultiplythefceintheprocess.Hereyoucanseethesimplestpossiblehydraulicsystem:YourbrowserdoesnotsupptJavriptitisdisabled.Simplehydraulicsystemlef

7、t.Thismeansthatanyfceappliedtothelefthpistonwillcomeoutninetimesgreaterontherighthpiston.Soifyouapplya100pounddownwardfcetotheleftpistona900poundupwardfcewillappearontheright.Theonlycatchisthatyouwillhavetodepresstheleft

8、piston9inches(22.86cm)toraisetherightpiston1inch(2.54cm).ASimpleBrakeSystemBefewegetintoallthepartsofanactualcarbrakesystemletslookatasimplifiedsystem:YourbrowserdoesnotsupptJavriptitisdisabled.AsimplebrakesystemYoucanse

9、ethatthedistancefromthepedaltothepivotisfourtimesthedistancefromthecylindertothepivotsothefceatthepedalwillbeincreasedbyafactoffourbefeitistransmittedtothecylinder.Youcanalsoseethatthediameterofthebrakecylinderisthreetim

10、esthediameterofthepedalcylinder.Thisfurthermultipliesthefcebynine.Alltogetherthissystemincreasesthefceofyourfootbyafactof36.Ifyouput10poundsoffceonthepedal360pounds(162kg)willbegeneratedatthewheelsqueezingthebrakepads.Th

11、ereareacoupleofproblemswiththissimplesystem.WhatifwehavealeakIfitisaslowleakeventuallytherewillnotbeenoughfluidlefttofillthebrakecylinderthebrakeswillnotfunction.Ifitisamajleakthenthefirsttimeyouapplythebrakesalloftheflu

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