Rotational-Motion(转动)

Chapter8rotationalmotion第1页共7页Kinematics1.Whatistheangulardisplacementofeachofthefollowinghandsofaclockin1h?Stateyouranswerinthreesignificantdigits.(a).thesecondhand.(b).theminutehand.(c).thehourhand.2.Arotatingtoyaboveababy’scribmakesonecompletecounterclockwiserotationin1min.A.Whatisitsangulardisplacementin3min?B.Whatisthetoy’sangularvelocityinrad/min?C.Iftheboyisturnedoff,doesithavepositiveornegativeangularacceleration?Explain.3.Ifatruckhasalinearaccelerationof1.85m/s2andthewheelshaveanangularaccelerationof5.23rad/s2,whatisthediameterofthetruck’swheels?4.Thetruckinthepreviousproblemistowingatrailerwithwheelsthathaveadiameterof48cm.a.Howdoesthelinearaccelerationofthetrailercomparewiththatofthetruck?b.Howdotheangularaccelerationsofthewheelsofthetrailerandthewheelsofthetruckcompare?5.Youwanttoreplacethetiresonyourcarwithtiresthathavealargerdiameter.Afteryouchangethetires,fortripsatthesamespeedandoverthesamedistance,howwilltheangularvelocityandnumberofrevolutionschange?6.IftheradiusofaCDis6.0cmandtheangularvelocityis5.0rad/s.Whatisthelineardisplacementofapointontheedgeis2.0s?(A).0.30m(B).0.60m(C).3.8m(D).60mTorque1.Adoor(seenfromaboveinthefiguresbelow)hashingesonthelefthandside.Whichforceproducesthelargesttorque?Themagnitudesofallforcesareequal.Chapter8rotationalmotion第2页共7页2.Arodonahorizontaltabletopispivotedatoneendandisfreetorotatewithoutfrictionaboutaverticalaxis,asshown.AforceFisappliedattheotherend,atanangletotherod.IfFweretobeappliedperpendiculartotherod,atwhatdistancefromtheaxisshoulditbeappliedinordertoproducethesametorque?(A)Lsin(B)Lcos(C)L(D)Ltan3.InwhichofthefollowingdiagramsisthetorqueaboutpointOequalinmagnitudetothetorqueaboutpointXinthediagram?(Allforceslieintheplaneofthepaper.)4.A5-meteruniformplankofmass100kilogramsrestsonthetopofabuildingwith2metersextendedovertheedgeasshown.Howfarcana50-kilogrampersonventurepasttheedgeofthebuildingontheplankbeforetheplankjustbeginstotip?(A)0.5m(B)1m(C)1.5m(D)2m5.Auniformmeterstickofmass0.20kgispivotedatthe40cmmark.Whereshouldonehangamassof0.50kgtobalancethestick?(A)16cm(B)36cm(C)44cm(D)46cm6.Toweighafish,apersonhangsatackleboxofmass3.5kilogramsandacoolerofmass5kilogramsfromtheendsofauniformrigidpolethatissuspendedbyaropeattachedtoitscenter.Thesystembalanceswhenthefishhangsatapoint1/4oftherod’slengthfromthetacklebox.Whatisthemassofthefish?(A)1.5kg(B)2kg(C)3kg(D)6kgChapter8rotationalmotion第3页共7页7.Twoobjects,ofmasses6and8kilograms,arehungfromtheendsofastickthatis70cmlongandhasmarksevery10cm,asshown.Ifthemassofthestickisnegligible,atwhichofthepointsindicatedshouldacordbeattachedifthestickistoremainhorizontalwhensuspendedfromthecord?(A)A(B)B(C)C(D)D8.Asquarepieceofplywoodonahorizontaltabletopissubjectedtothetwohorizontalforcesshown.Whereshouldathirdforceofmagnitude5newtonsbeappliedtoputthepieceofplywoodintoequilibrium?9.AwheelofradiusRandnegligiblemassismountedonahorizontalfrictionlessaxlesothatthewheelisinaverticalplane.Threesmallobjectshavingmassesm,M,and2M,respectively,aremountedontherimofthewheel,asshown.Ifthesystemisinstaticequilibrium,whatisthevalueofmintermsofM?(A)M/2(B)M(C)3M/2(D)5M/210.Asystemoftwowheelsfixedtoeachotherisfreetorotateaboutafrictionlessaxisthroughthecommoncenterofthewheelsandperpendiculartothepage.Fourforcesareexertedtangentiallytotherimsofthewheels,asshown.Themagnitudeofthenettorqueonthesystemabouttheaxisis(A)zero(B)2FR(C)5FR(D)14FRRotationalKinematicsandDynamics1.Twosmall“weights,”ofmass5.0kgand7.0kg,aremounted4.0mapartonalightrod(whosemasscanbeignored),asshowninFig.Calculatethemomentofinertiaofthesystem(a)whenrotatedaboutanaxishalfwaybetweentheweights,Figa,and(b)whenrotatedaboutanaxis0.50mtotheleftofthe5.0-kgmass(Fig)Chapter8rotationalmotion第4页共7页2.A15.0-Nforce(representedbyFT)isappliedtoacordwrappedaroundapulleyofmassM=4.00kgandradiusR=33.0cmFig.Thepulleyacceleratesuniformlyfromresttoanangularspeedof30.0rad/sin3.00s.Ifthereisafrictionaltorqueτfr=1.10m·Nattheaxle,determinethemomentofinertiaofthepulley.Thepulleyrotatesaboutitscenter.3.AuniformstickhaslengthL.ThemomentofinertiaaboutthecenterofthestickisIo.AparticleofmassMisattachedtooneendofthestick.Themomentofinertiaofthecombinedsystemaboutthecenterofthestickis(A)2014IML(B)2012IML(C)2034IML(D)20IML4.Alightrigidrodwithmassesattachedtoitsendsispivotedaboutahorizontalaxisasshownabove.Whenreleasedfromrestinahorizontalorientation,therodbeginstorotatewithanangularaccelerationofmagnitude(A)gl7(B)gl5(C)gl4(D)57gl5.Twoblocksarejoinedbyalightstringthatpassesoverthepulleyshownabove,whichhasradiusRandmomentofinertiaIaboutitscenter.T1andT2arethetensionsinthestringoneithersideofthepulleyandαistheangularaccelerationofthepulley.Whichofthefollowingequationsbestdescribesthepulley'srotationalmotionduringthetimetheblocksaccelerate?(A)m2gR=Iα(B)T2R=Iα(C)(T2-T1)R=Iα(D)(m2–m1)gR=IαEquilibrium，CentermassandStability1.Anon-uniformplankofwoodXYis2.50mlongandweighs950N.Force-meters(springbalances)AandBareattachedtotheplankatadistanceof0.40mfromeachend,asillustratedinFig.Chapter8rotationalmotion第5页共7页Whent