GRE-subject-physics-分类练习题(含答案解析)

11.AsatelliteorbitstheEarthinacircularorbit.AnastronautonboardperturbstheorbitslightlybybrieflyfiringacontroljetaimedtowardtheEarth’scenter.Afterward,whichofthefollowingistrueofthesatellite’spath?(A)Itisaellipse.(B)Itisahyperbola.(C)Itisacirclewithlargerradius.(D)Itisaspiralwithincreasingradius.(E)Itexhibitsmanyradialoscillationsperrevolution.A2.ApersonstandingonthesurfaceoftheEarththrowsaball.Theballleavesthethrower’shandwithinitialvelocityviandhasfinalvelocityvfjustbeforeitiscaught.Ifairresistanceisnegligible,whichofthefollowingdiagramscorrectlyrepresentsapossiblesequenceofvelocityvectorsfortheball?VerticalHorizontalVerticalHorizontalVerticalHorizontalVerticalHorizontalVerticalHorizontal(A)(B)(C)(D)(E)E(E)mh3.Asshownabove,ablockofmassmisreleasedfromrestatadistancehaboveaverticalmasslessspringwithspringconstantk,whatisthemaximumkineticenergyoftheblock?(A)mgh(B)kgmmgh2241+(C)kgmmgh2221+(D)kgmmgh22+(E)2mgh0=dtdvxkxmg=kmgx=()222121kxmvxhmg+=+x()kgmmghkxxhmgmvEk221212222+=−+==C2MvmvB=0BeforeAfter4.AbulletofmassmtravelingatspeedvstrikesablockofmassM,initiallyatrest,andisembeddedinitasshownabove.Howfarwilltheblockwiththebulletembeddedinitslideonaroughhorizontalsurfaceofcoefficientofkineticfrictionµkbeforeitcomestorest?(A))2)((2gvmMmkµ+(B))2)((2gvMMmkµ+(C))2()(22gvMMmkµ+(D))2)((2gvMmmkµ+(E))2()(22gvMmmkµ+()VMmmv+=()()gsMmVMmk+=+µ221222))(2(2MmmgvgVskk+==µµE2kgθF=10N5.A2-kilogromboxhangsbyamasslessropefromaceiling.aforceslowlypullstheboxhorizontallytothesideuntilthehorizontalforceis10newtons.Theboxisthenequilibriumasshownabove.Theanglethattheropemakeswiththeverticalisclosestto(A)arctan0.5(B)arcsin0.5(C)arctan2.0(D)arcsin2.0(E)45°20N5.0arctan2010arctan==θA6.A5-kilogramstoneisdroppedonanailanddrivesthenail0.025meterintoapieceofwood.Ifthestoneismovingat10meterspersecondwhenithitsthenail,theaverageforceexertedintothewoodismostnearly(A)10N(B)100N(C)1000N(D)10,000N(E)100,000NN10000025.0/10521/2122=××==hmvFD7.Amachinegunfiresbulletsofmass20gramseachatarateof1200bulletsperminute.Thebulletshitathickwoodentargetataspeedof600meterspersecondandarestoppedinthetarget.Theaverageforceexertedonthetargetbythebulletsstrikingitis(A)144N(B)240N3(C)14.4103N(D)24.0103N(E)14.4103NPFdt∆=∫N24060600120010203=×××=∆∆=−tmVF(B)Questions8-9RMrAuniformcylindricalpuckofradiusrandmassMisattachedtotheendofacordthatpassesthroughaholeinafixedhorizontalfrictionlesstableasshownabove.ThecenterofthepuckmovesinacircleofradiusRwithangularspeedω8.Themagnitudeoftheangularmomentumofthepuckabouttheholeis(A)223RMω(B)ω)(22rRM+(C)22122)(ωrRM+(D)ω)21(22rRM+(E)22122)21(ωrRM+221MrI=222021MRMrMRII+=+=22122)21(ωωrRMIL+==E9.Ifthestringispulledslowlydownwardsothatthecenterofthepuckmovesinacircleofsmallerradius,quantitiesthatareconservedincludewhichofthefollowing?I.AngularmomentumII.LinearmomentumIII.Kineticenergy(A)Ionly(B)IIIonly(C)IandIIonly(D)IIandIIIonly(E)I,II,andIIIIII221ωIconstant=ωIIIIA10.Anexpressionforthepotentialenergyoftwoionsis92..rbrkqEP+−=.Whatistheconstantbasafunctionoftheequilibiumspacingr0?(A)1002rkq(B)02rkq4(C)0298rkq(D)1002rkq(E)9802rkqr0091022..=−=rbrkqdrdUEP2809kqbr=9802rkqb=E11.Arigidcylinderrollsatconstantspeedwithoutslippingontopofahorizontalplanesurface.Theaccelerationofapointonthecircumferenceofthecylinderatmomentwhenthepointtouchestheplaneis(A)directedforward(B)directedbackward(C)directedup(D)directeddown(E)zero(C)Questions12-13Acylinderwithmomentofinertia4kg⋅m2aboutafixedaxisinitiallyrotatesat80radianspersecondaboutthisaxis.Aconstanttorqueasappliedtoslowitdownto40radiuspersecond.12.Thekineticenergylostbythecylinderis(A)80J(B)800J(C)4000J(D)9600J(E)19,200J221ωωIT=()()J96004080421'2122220=−××=−=∆ωωIT(D)13.Ifthecylindertakes10secondstoreach40radiuspersecond,themagnitudeoftheappliedtorqueis(A)80N⋅m(B)40N⋅m(C)32N⋅m(D)16N⋅m(E)8N⋅mβIM=MβmN161040804'0⋅=−×=−==tIIMωωβDQuestions14-15Anonrelativisticparticleofmassmmovesinaplane.Itspositionisdescribedbythepolarcoordinatesrandθ,withtimederivativesr&andθ&.ThereexistsapotentialenergyU=kr2,wherekisaconstant.14.WhichofthefollowingistheLagrangianoftheparticle?(A)()222221krrrmL−+=θ&&(B)()22221krrmL++=θ&5(C)()2222221krrrmL−+=θθ&&(D)()222221krrrrrmL−++=θθ&&&&(E)()2222221krrrrrmL−++=θθ&&&&LagrangeVTL−=θθeev&&rrr+=()()2222222121krrrmVvvmVTLr−+=−+=−=θθ&&(A)15.Whichofthefollowingquantitiesremainsconstant?(A)()222θ&&rrm+(B)22θ&mr(C)2kr(D)θ&mr(E)θ&2mrrFˆ2krdrdU==2krU=θθ&rθ&2mr(E)16.Aballdroppedfromaheighth.Asitbouncesoffthefloor,itsspeedis80percentofwhatitwasjustbeforeithitthefloor.Theballwillthenrisetoaheightofmostnearly(A)0.94h(B)0.80h(C)0.75h(D)0.64h(E)0.50hmghmv=22164.08.0''22==⎟⎠⎞⎜⎝⎛=vvhh(D)m1m2x17.Twomasses,m1andm2,arejoinedbyamasslessspringofforceconstantkandplacedonahorizontalfrictionlesssurfaceasshownabove.Thesystemisreleasedfromrestwhentheseparationbetweenthemassesisx.Iftheunstretchedlengthofthespringisx0,thespeedofmassm1whenthetwomassesareadistancex0apartis(A)201)(xxmk−(B)202)(xxmk−(C)2021)(xxmmk−+(D)202121)(xxmmmmk−+⋅(E)202112)(xxmmmmk−+⋅v1v22211vmvm=6()22221120212121vmvmxxk+=−2021211)(xxmmmmkv−+⋅=(D)17.What