问题 问答题

篮球从手中落到地上又弹跳起来,你能说出这一过程中的能量转化情况吗?

答案

答:

第一阶段:篮球从手中下落直到接触地面的瞬间,球的高度越来越小,速度越来越大,由此可以判断球的重力势能逐渐减小,动能逐渐增大,重力势能转化为动能。

第二阶段:篮球从接触地面的瞬间到发生弹性形变的程度最大,球的速度逐渐减小,弹性形变的程度逐渐增大,由此可以判断球的动能逐渐减小,弹性势能逐渐增大,动能转化为弹性势能。

第三阶段:篮球从弹性形变的程度最大到恢复原状的过程中,球的弹性形变的程度在减小,向上的速度逐渐增加,由此可以判断球的弹性势能逐渐减小,动能逐渐增加,弹性势能转化为动能。

第四阶段:篮球从离开地面的瞬间到上升至最高点,球的速度逐渐减小,高度越来越大,由此可以判断球的动能逐渐减小,重力势能逐渐增大,动能转化为重力势能。

完形填空
I’m glad it’s Sunday again. I can stay in bed   36 I like, drinking tea and   37   those thick newspapers that are brought  38  the newsboy through the letterbox at 8:30. In this way, I can catch up with all the   39  I haven’t got time to read during my work time.
When I   40  the papers, I then prepare my bath. The Sunday morning bath is   41  of the week. There’s no need to hurry because there’s no bus to   42  and my friends are told not to call me up before noon on Sundays, so there is no danger of   43    by the telephone.
  44 spend the afternoon after lunch is always a bit of problem. In summer I can go to the park and sit in a chair   45  boys playing football, while in winter I sit in front of the fire and   46   when reading a book, sometimes I turn on the television and sleep through an old film.  
Then there’s the   47 ahead of me. Perhaps I’ll call on some friends or go to the cinema   48   a new film I want to see or to town for a concert. Oh, there are   49   pleasant ways of passing Sunday evenings. The only sad thing is that Monday morning is getting    50 .
小题1:
A.as long asB.as soon asC.as well asD.as much as
小题2:
A.readB.readingC.to readD.am reading
小题3:
A.fromB.withC.andD.by
小题4:
A.thingsB.booksC.informationD.knowledge
小题5:
A.am readingB.have readC.had readD.read
小题6:
A.the much pleasantB.the more pleasant
C.the most pleasantD.the very pleasant
小题7:
A.sitB.catchC.get inD.take
小题8:
A.troubleB.being troubledC.troublingD.to be troubled
小题9:
A.What toB.How toC.When toD.Where to
小题10:
A.lookingB.seeingC.looking atD.watching
小题11:
A.fall asleepB.go to sleepC.go to bedD.get to sleep
小题12:
A.supperB.friendC.eveningD.work
小题13:
A.whether there’sB.if there is
C.when there hasD.if there will be
小题14:
A.so manyB.such manyC.a lotD.quite few
小题15:
A.busierB.longerC.nearD.away
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