一质点在铅垂平面内作圆周运动，当质点恰好转过一周时，其重力的功为零，对吗?为什么?
对的。因为重力的功等于质点的质量与其始末位置的高度差的乘积，当高度差为零时，重力的功为零。
暂无解析
Thepoliceman[halted]thespeedingcartoseeifthedriverwasdrunk.
Yoursister_______tovisityouquiteofen,didn'tshe?
ReadingComprehension
SectionA
Directions:Therearetenincompletesentencesinthissection.ForeachsentencetherearefourchoicesmarkedA,B,CandD.ChoosetheONEthatbestcompletesthesentence.Thenwritedowntherightanswerinthebracketsforeachsentence.Thissectiontotals10points,onepointforeachsentence.
()1.Wecansupplyallthebicyclesyourequired____________stockandarearrangingshipmentbyM.V.Mermaid.
A.forB.from C.to D.against
()2.Wewouldliketoremindyouthatthe__________L/CmustreachusbeforeMarch10
sothatwecanmakeshipmentingoodtime.
A.coveringB.cover C.coveredD.beingcovered
()3.Wehavereceivedyourletterof28March,___________ustomodifythepreviousarrangementsfortheshipmentofthecaptionedorder.
A.askedB.toask C.beingaskedD.asking
()4.InourletterofMay5,wemade__________clearthatshipmentistobeeffectedinJune.
A.youB.them C.thatD.it
()5.Wealwaysdeal_______________paymentbysightL/C.
A.with B.in C.at D.on
()6.Thisofferis_____________toyourreplyreachingusbeforethe20thofFebruary.
A.subjectingB.subject C.subjectedDtosubject
()7.____________weareappreciatingthegoodqualityofyourblacktea,weregretthatyourpriceappearstobeonthehighside.
A.WhileB.When C.HoweverD.Therefore
()8.Weherebyauthorizeyouto___________onusat60daysaftersighttotheextentofUSD20,000.00.
A.open B.establish C.draw D.build
()9.Ifpartiestoacontractdesiretosettledisputes,anarbitrationclauseisusuallymadeinthecontractwellbeforeadispute_____________.
A.risesB.arisesC.lookD.appear
()10.Somecustomersrequestedusto_____________ourpricebecausetheyconsideredit
toohigh.
A.putdownB.getdownC.takedown D.bringdown
Theoldmanlivesinavillage_______,butheneverfeels________.
Weallfound_____toplaythegame.
