题目

在利用悬线悬挂等大小球探究碰撞中的不变量的实验中，下列说法不正确的是( )A．悬挂两球的细绳长度要适当，且等长B．由静止释放小球，以便较准确计算小球碰前速度C．两小球必须都是钢性球，且质量相同D．两小球碰后可以粘在一起共同运动 答案：【答案】C【解析】两小球无论是弹性球还是非弹性球动量都是守恒的，C错；Linda, Tony, Harry, David 和Lucy都非常喜欢读书，请仔细阅读题中的个人情况说明和A—F六本书的介绍，选出符合各自要求的最佳选项。【小题1】 Linda is a 11-year-old girl. She likes nature. In spring, she enjoys going out. In summer, she likes swimming. She also loves to read something about nature, especially books about animals.【小题2】Tony is 20. His dream is to be a doctor. Besides medicine books, she likes to read some stories about famous people.【小题3】Harry is 35 years old. He works in a middle school. He does a part-time job as a translator. He likes to translate some English short stories into Chinese. He often reads many English magazines and books. Now he wants to translate an English novel.【小题4】 David is 64 years old. His job is a manager. But he is overweight. With too much work to do, his health is poor. To keep fit, he does more sports every day. What’s more, he wants to read some books about health in the evening.【小题5】 Lucy is young and beautiful. She likes fashion. She always reads fashion books. Besides these, she has a big dream. She wants to be good at handwriting, so she needs a book about handwriting.A． Introduction: - Context: An English novel about a war. It hasn’t had a Chinese edition(版本)yet. If you are good at translating, you can have a try.- Price: $5B． Introduction: - Context: It writes some funny stories about the sea. It shows how the sea animals live. Nature lovers can read the book.- Price: $1C． Introduction: - Context: A book about handwriting. You can practice your handwriting according to this book.- Price: $1.5D． Introduction: - Context: You can read something about health. If you want to keep fit, the book is a good choice for you.- Price: $2E.  Introduction:   - Context: You can get some knowledge about stamps. It will bring you a wonderful world.- Price: $2.5F.  Introduction:    - Context: Helen Keller is a famous educator. If you want to know her life, this book is for you.- Price: $3