问题 问答题

“神舟十号”飞船在绕地球做匀速圆周运动时,离地面的高度为h,周期为T,已知地球的半径为R,引力常量为G,则地球的质量和密度分别是多大的.(球的体积公式:V=

4
3
πR3,其中R为球的半径)

答案

根据万有引力等于向心力,有:G

Mm
(R+h)2
=m
4π2
T2
(R+h)

得:M=

4π2(R+h)3
GT2

因为地球的体积为:V=

4
3
πR3

得:ρ=

M
V
=
3π(R+h)3
GT2R3

答:地球质量为

4π2(R+h)3
GT2
,密度为
3π(R+h)3
GT2R3

阅读理解

阅读理解。

     The teacher was giving the students a written exam (写作测验). He wanted them to write a composition

(作文)- "My Dog", no less than(不少于) 150 words.

     Little Tommy thought for a minute. Then he wrote "I have a dog. I call (叫做) him Bobby. I like my dog.

He is all black, only the nose is white …"Tommy stopped writing and counted (数) the words - 21. He

scratched(搔,抓) his head, thought for a few minutes and went on (继续……)."Every day, I take Bobby out

for a walk in the park. But when it rains, I do not take him out for a walk."Another 24 words. Tommy

scratched his head again, looked at the ceiling(天花板), then looked at the blackboard. He found nothing there.

He sighed (叹了一口气). Suddenly an idea came to him. He smiled (微笑) happily, and wrote quickly,"When

I want Bobby to come to, I call Bobby!Bobby! Bobby! If he still does not come, I just shout (大声地叫),

Bobby!Bobby! Bobby! Bobby…!" Tommy counted the words 149. He added(加) one more"Bobby", wrote

down his name and handed it in(hand in 上交) to the teacher.

1. The teacher asked the students to write a composition about _____.

A. my dog

B. Tommy

C. Bobby

D. a dog

2. Tommy found _____ on the ceiling.

A. an idea

B. a dog

C. nothing

D. some words

3. Which word comes most in Tommy's composition?

A. Dog

B. Bobby

C. I

D. He

4. Tommy's composition is _____ words.

A. 24

B. 45

C. 149

D.150

5. Choose (选择) the topic (题目) for the passage.

A. A composition

B. An Exam

C. My Dog

D. Bobby

选择题