问题
探究题
如图所示，将两个一次性纸杯杯口向上叠套起来，用手握住外面的纸杯，在靠近杯口的上方平行于杯口方向用力吹气。
（1）请你猜测里面的纸杯将 [ ]
A．保持静止
B．发生旋转
C．压得更紧
D．向上跳起
（2）你的猜测依据是： 。
答案
（1）D
（2）杯口上方空气流速增大，压强减小，使里面杯子所受向下的气压小于所受向上的气压。
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如图所示，将两个一次性纸杯杯口向上叠套起来，用手握住外面的纸杯，在靠近杯口的上方平行于杯口方向用力吹气。
（1）请你猜测里面的纸杯将 [ ]
A．保持静止
B．发生旋转
C．压得更紧
D．向上跳起
（2）你的猜测依据是： 。
（1）D
（2）杯口上方空气流速增大，压强减小，使里面杯子所受向下的气压小于所受向上的气压。
| 完形填空。 |
| John lived with his mother in a very big house, and when she 1 , the house became too big 2 him, so he bought a 3 one in the next street. There was a very nice, old clock in his 4 house, and when the man came to take his things to the new house, John thought, "I'm not going to let them 5 my beautiful old clock in their truck. Perhaps they will break it, and then it will be very expensive to repair it." So he 6 and began to carry it down the road in his arms. It was heavy, so he stopped two or three times to have 7 . Then suddenly a small boy came along the road. He stopped and looked at John for 8 seconds. Then he said to John, "You're a 9 , aren't you? 10 don't you buy a watch like everyone else?" |
| ( )1. A. worked ( )2. A. at ( )3. A. larger ( )4. A. second ( )5. A. to carry ( )6. A. picked it up ( )7. A. a look ( )8. A. a few ( )9. A. great ( )10. A. Where | B. studied B. with B. bigger B. third B. bring B. picks it up B. a drink B. few B. fool（傻瓜） B. Why | C. died | D. played D. for D. smaller D. new D. carry D. picked up it D. a rest D. a little D. bright D. When |