问题 选择题

如图所示,在不光滑的平面上,质量相等的两个物体AB间用一轻弹簧相连接,现用一水平拉力F作用在B上,从静止开始经一段时间后,AB一起做匀加速直线运动,当它们的总动能为Ek时撤去水平力F,最后系统停止运动,从撤去拉力F到系统停止运动的过程中,系统(   )

                            

①克服阻力做的功等于系统的动能Ek

②克服阻力做的功大于系统的动能Ek

③克服阻力做的功可能小于系统的动能Ek

④克服阻力做的功一定等于系统机械能的减少量

A.①②

B.③④

C.②④

D.①④

答案

C   

当A、B一起做匀加速直线运动时,弹簧一定处于伸长状态,因此当撤去外力F到系统停止运动的过程中,系统克服阻力做功应包含系统的弹性势能,因此可以得  知①②正确.

完形填空
One of my. next-door neighbor is a sweet 92-year-old Polish lady. A few days ago, I came back from a trip. As I was  16 . my clothes in my room, I heard a(n)  17  , frantic(发疯的) knock on the door. It was 10:30 pm, and I wasn’t sure who it could be. I went downstairs and  18  the peephole, and saw that it was our sweet next-door neighbor.
I quickly  19  the door, and she seemed really distressed and kept  20 , Please help me. I need your help. The fire alarm won’t go off. Please help me.” I  21  told her that everything would be okay, and  22  her to her house to see what was going on  23  the fire alarm.
She  24  that the alarm had been going on and off inconsistently(反复无常的) for the past two hours, and that her  25  to call her daughter to come and fix it was fruitless. So I took a chair from her dining room table,  26  it, and looked at the tire alarm.
After twisting the fire alarm off, I blew into it, because sometimes  27  causes it to make strange noises. She seemed  28  but was literally shaking out of fear. I asked her  29  she was okay, and she said she was  30  , so I gave her a hug. I felt her shaking in my embrace, and held her  31  for a few minutes until she stopped shaking and sighed a breath of relief.
We then  32  and talked for ten minutes, until I felt that she was okay. and safe to sleep. She was so generous with  33  for being with her, but I thanked her for  34  me that hugs are indeed good tools! So, sometimes, a(n)  35  hug is a good and powerful way to hold someone going through a difficult period.
小题1:
A.collecting B.designingC.unpackingD.setting
小题2:
A.constant B.flexibleC.rhythmicD.impressive
小题3:
A.looked through B.made outC.cut offD.turned to
小题4:
A.closed B.movedC.lockedD.opened
小题5:
A.thinking B.repeatingC.complainingD.screaming
小题6:
A.frequently B.brieflyC.immediatelyD.roughly
小题7:
A.required B.accompaniedC.inspectedD.observed
小题8:
A.for B.toC.byD.with
小题9:
A.predicted B.warnedC.mentionedD.proved
小题10:
A.attempt B.suggestionC.responsibilityD.permission
小题11:
A.pressed B.revolvedC.crashedD.climbed
小题12:
A.powerB.dustC.paperD.switch
小题13:
A.determinedB.terrifiedC.relievedD.devoted
小题14:
A.whenB.howC.whyD.if
小题15:
A.afraidB.tiredC.sleepyD.pleased
小题16:
A.casuallyB.tightlyC.automaticallyD.abruptly
小题17:
A.broke downB.sped upC.sat downD.turned around
小题18:
A.suffering B.regret C.shame D.gratitude
小题19:
A.advising B.reminding C.encouraging D.advocating
小题20:
A.simple B.special C.official D.sudden
单项选择题