问题 选择题

一枚火箭搭载着卫星以速率v0进入太空预定位置,由控制系统使箭体与卫星分离。已知前部分的卫星质量为m1,后部分的箭体质量为m2,分离后箭体以速率v2沿火箭原方向飞行,若忽略空气阻力及分离前后系统质量的变化,则分离后卫星的速率v1     。(填选项前的字母)

A.v0-v2

B.v0+v2

C.

D.

答案

答案:D

题目分析:系统分离前后,动量守恒:,解得:,故A、B、C错误;D正确。

阅读理解

Nothing was going right for Dr. Turner at the hospital. He made a mistake while operating on a patient. He felt sure he was no longer trusted and decided to change his job. One day he learned from the paper that a doctor was looking for a partner(合作伙伴). The doctor, whose name was Johnson, lived in Thorby, a small town in the north of England.

A few days later Dr. Turner went to Thorby, and arrived at Dr. Johnson’s home early in the afternoon. Though old and a little deaf, Dr. Johnson still had a good brain. He kept talking to the visitor about the town and its people. When they turned to the question of partnership, it was already seven in the evening. Dr. Johnson invited Dr. Turner to have dinner with him in a restaurant before catching the train back to London. Dr. Turner noticed that Dr. Johnson was fond of good food and expensive wines. They had an excellent meal. When the bill was brought, Dr. Johnson felt in his pocket. “Oh, dear,” he said. “I’ve forgotten my money.” “That’s all right,” Dr. Turner said. “I’ll pay the bill.” As he did so, he began to wonder whether Dr. Johnson was worthy of trust.

小题1:Dr. Turner knew that a doctor was looking for a partner from______.

A.the Internet

B.the newspaper

C.the radio

D.the magazine小题2: Dr. Turner decided to leave his present job because_______.

A.he had never been trusted

B.it needed too great skills

C.he believed it offered little hope for his future

D.he thought the hospital would like him to leave小题3:The two doctors spent most of the afternoon talking about_______.

A.things of no interest to Dr. Johnson

B.things of no importance to Dr. Turner

C.health matters

D.food and drink小题4:The story suggests that_______.

A.Dr. Johnson did not like Dr.Turner

B.The two doctors would become friends

C.The two doctors would not work together

D.Dr. Turner decided to stay at his present job小题5:The words did so in the last sentence mean_______.

A.caught the train back to London

B.felt in his pocket

C.paid the bill

D.said those words

填空题