阅读理解。
The big red American car was much too wide for an English country road. When Jack saw it coming
toward him. he stopped his own car at the side if the road to make room for it to past. The American car went
slowly past, so close that he could see the driver's face quite clearly.
"Where have I seen that face before?" he thought., ''Wait a minute! I remember now. It was in the
newspaper!'"He took out the newspaper from his bag, turned quickly to the middle page. There was a picture
of the face in it. Yes, it bad a large mouth and small ears., and his eyes were behind dark glasses.
"Wanted by the police," read by Jack. "The City Bank will give a lot of money to anyone who helps the
police to catch this man.."
"Call the police at once," he said to himself. But a few minutes later, he was sad. "This man was caught this
morning," answered the police..
1. In which country did the story happen?
A. It happened in America.
B. It happened in Australia.
C. It happened in England.
D. The story didn't tell us.
2. Why did Jack stop his car?
A. He wanted to see who the driver was.
B. He didn't want to pass by first.
C. The road was too narrow for the two cars to pass at the same time.
D. Because it was good for an Englishman to stop to let other go.
3. Who was wanted by the police in this passage?
A. Jack.
B. The driver in the American car.
C. Either Jack or the driver.
D. Neither Jack nor the American driver.
4. What did Jack do when he had read the newspaper again?
A. He drove to the City Bank.
B. He drove to the police.
C. He made a telephone call.
D. He stopped the American car.
5. Who caught the man with a large mouth and small ears?
A. The police.
B. Jack.
C. Nobody.
D. The American driver.
，且有：
，计算得
，将b物体隔离受力分析并计算，有
，所以此时b物体受到三个力，A选项正确；当两个集装箱一起向上匀加速直线运动时，有：
，计算得
，再将b物体隔离出来受力分析，利用假设法，如果b物体受到其它力，加速度将
，与整体的加速度矛盾，则b物体此时也只受到三个力，B选项错误；据以上分析，如果传送带突然停止，则b物体的状态与整体的状态一样，将只受到三个力，如果物体原来做匀速运动，则传送带停止前后b物体的摩擦力均为f ’=
，如果物体原来匀加速运动，物体和传送带之间有相对运动，摩擦力为
=f，物体停止运动相对传送带静止时，摩擦力为
<f，可见，传送带停止后物体摩擦力等于后小于停止前的摩擦力，所以C、D选项错误。