题目

 如图所示，a、b是两颗质量相等，绕地球做匀速圆周运动的卫星，下列说法正确的是 A. 卫星a的动能大于b的动能 B. 卫星a的动能小于b的动能 C. 卫星a的机械能大于b的机械能 D. 卫星a机械能小于b的机械能 答案：BC 【解析】AB. 根据 可知，半径小的b线速度更大，质量相同，所以b的动能更大，A错误B正确． CD. 引力势能的表达式 ，根据万有引力提供向心力得，动能 ，总的机械能 所以半径大的a机械能更大，C正确D错误．任务型阅读（本题共5小题，每小题1分，共5分）请阅读1-5题中的内容，并根据内容与A-F 进行匹配。1.Jen loves pets. She often goes to help look after some pets with the animal doctors.One day, she would like to work as an animal doctor too.2. Zhao Ting is a teacher from China and she has stayed in the US for a short time. She likes the country very much. She can speak perfect English and she will stay there and work as a teacher.3.David is the boss of a big education company in England. He wants to set up another company in China because he thinks a large number of people in China may join this field and as a result he can make more money.4.Lin Jun has just come back from England. He is now looking for a job. He wants to work in a big company.5.Jenny is a housewife. She goes to the food market every day. She always wants to buy different kinds of fresh food at a low price.A. We need someone who can teach Chinese here and of course, you must speak good English. It’s better for you to have some teaching experience.B. Lots of people have pets and their pets sometimes get ill. They need to find some people to help them get well.C. Chinese parents think education is really important and they always save money for children’s education. As a result, the education market is very big in China.D. We sell eggs, apples, tomatoes and other healthy food at very low prices. Our opening hours are from 6：00 am to 10：30.E. It’s not easy to win an English speaking competition. Read more books about speaking and you will get lots of help from them.F. Many big companies today need workers who can speak English or has the experience of living or working in another country.