题干

如图所示是蹦极运动的简化示意图,弹性绳一端固定在O点,另一端系住运动员,运动员从O点自由下落,到A点处弹性绳自然伸直.B点是运动员受到的重力与弹性绳对运动员拉力相等的点,C点是蹦极运动员到达的最低点(忽略空气阻力),下列说法正确的是(    )

A:从O点到C点运动员速度一直减小

B:从O点到C点运动员的机械能一直在增大

C:从O点到C点运动员的机械能一直在减小

D:从O点到A点运动员的机械能不变

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D

同类题3

完型填空。

Tom and Steve were twin brothers. Tom loved to play basketball. But Steve loved to read books. One day Tom was playing basketball    21  he fell and broke his leg. When they took him to the hospital, the doctor said he wouldn’t be able to play for six months. Steve went    22  him to and brought him books on basketball. At first Tom wasn’t going to read them. Then he began to read them and 23 that there were ways he could play basketball better. He began to think that books weren’t    24  .

    When Tom’s leg started getting better, Steve would help him by going for walks with him.  25 Tom’s doctor said he could start playing basketball again. Then Tom showed Steve how to toss(投)for baskets. Steve found that he enjoyed it.

    Then Tom was ready to   26   the basketball games. Steve went to watch the games and enjoyed himself. They then    27   practiced basketball and read books together.

    So you can see, when    28    happens, something good may also happen. Steve showed Tom about books and Tom showed Steve about basketball.

So you can also   29   showing others something that you like to do and they can show you something that they like to do. 30 you can find new things to do.

21A. until              B. when            C. after           D. where

22A. on seeing          B. to call            C. to visit         D.to look

23A. saw              B. looked            C. read           D. found

24A. good             B. bad              C. better           D. worse

25A. But              B. However          C. Finally         D. So

26A. take              B. win              C. lose            D. join in

27A. always            B. never            C. seldom          D. much

28A. anything good      B. something nice     C. something bad   D. anything wrong

29A. try               B. practice           C. enjoy          D. like

30A . On the way       B. By the way        C. In a way       D. In this way