问题 问答题

光滑水平面上放置一根质量为m的均质细杆MN,长为L,距M端1/4处的右侧固定了一颗钉子A,在靠近细杆N端的左侧放置一质量为m的小球B,现有一质量为m的小球C以垂直于细杆的水平速度V0撞向细杆的M端,如图所示。已知小球C与细杆相撞后粘附在M端,然后小球B与细杆发生的是完全弹性碰撞,求:

碰撞后,小球B的速度。

答案

参考答案:

小球B与细杆发生完全弹性碰撞满足角动量守恒和机械能守恒:

解得,方向与V0相反,略偏向M端。

阅读理解

阅读理解。

     Mr. Grey is a teacher of English. He is not a very young man, but he is not old, either. He knows three

  or four languages and reads and speaks and writes them well. He reads many books and writes some.

     His desk is in the middle of the room, pens, pencils and ink bottle are on the desk. There is some

 paper, too. The telephone is on the left. There is a reading-lamp behind the telephone. It is almost eleven

  o'clock at night now. But Mr. Grey is still working. He works very late. Sometimes he works till two or

 three o'clock in the morning. But usually he goes to bed at about twelve or one o'clock.

     He teaches his students very well. All of them like him. He is not only their teacher but also their friend.

1. According to the passage, Mr. Grey is an _____ teacher.

    A. old                    

    B. Geography        

    C. English              

    D. Math

2. From the passage we know Mr. Grey's languages are very _____ .

    A. good            

    B. fast          

    C. well          

    D. pretty

3. In the second paragraph, we know Mr. Grey works _____ .

    A. late at night                                  

    B. at noon        

    C. early in the morning                    

    D. for long time in the morning

4. Mr. Grey's _____ is wonderful.

    A. cooking        

    B. music          

    C. fishing          

    D. teaching

5. The passage is mainly about _____ .

    A. Mr. Grey's language                    

    B. the friendly teacher    

    C. Mr. Grey's family                        

    D. a good teacher

单项选择题