如图所示，P是位于水平粗糙桌面上的物块，用跨过光滑轻质定滑轮的轻绳将P与小盘相连

发布时间：2017-07-20 06:09 │ 来源：www.tikuol.com

题型：选择题

问题：

如图所示，P是位于水平粗糙桌面上的物块，用跨过光滑轻质定滑轮的轻绳将P与小盘相连，小盘内有砝码，小盘与砝码的总质量为m，在P向右加速运动的过程中，桌面以上的绳子始终是水平的，关于物体P受到的拉力和摩擦力的以下描述中正确的是

A．P受到的拉力的施力物体就是m，大小等于mg

B．P受到的拉力的施力物体不是m，大小等于mg

C．P受到的摩擦力方向水平向左，大小一定小于mg

D．P受到的摩擦力方向水平向左，大小有可能等于mg

完形填空。
Farley worked for the Canadian government. One day, he was __1__ to learn more about wolves. Do wolves kill lots of caribou(北美驯鹿) Do they kill people? They gave him lots of food and clothes and guns. Then they put him on a plane and took him to __2__. The plane put him down and went away. There were no houses or people in this place. But there were lots of animals and lots of wolves. People tell terrible stories about wolves. They say wolves like to kill and eat people. Farley remembered these stories, and he was __3__. He had his gun with him __4___. Then one day, he saw a group of wolves. There was a mother wolf with four baby wolves. A father wolf and another young wolf lived with them. Farley watched these wolves every day. The mother was a very __5__ mother. She gave milk to her babies. She gave them lessons about life. They learned how to __6__ food. The father wolf got food for the mother. The young wolf __7__ the children. They were a nice, happy family-wolf family! Farley did not need his __8__ any more. In a short time, he got on well with the family. Farley watched them for five months. He learned that many stories about the wolves were __9__. Wolves do not eat people, and they do not eat many large animals. And he also learned bad things about men. It was men who killed many caribou and wolves. Later, Farley wrote a book about wolves. He wanted people to __10__ them and not to kill them.
( ) 1. A. seen ( ) 2. A. a small town ( ) 3. A. afraid ( ) 4. A. at times ( ) 5. A. bad ( ) 6. A. cook ( ) 7. A. shouted at ( ) 8. A. food ( ) 9. A. not good ( ) 10. A. grow	B. told B. a big city B. happy B. all the time B. good B. make B. looked into B. clothes B. not true B. have	C. heard C. a far place C. angry C. once a week C. hungry C. get C. laughed at C. gun C. not easy C. teach	D. found D. a lonely village D. tired D. every afternoon D. thirsty D. pick D. played with D. plane D. not clear D. understand