问题 选择题

我国曾发射一颗绕月运行的探月卫星“嫦娥1号”。设想“嫦娥1号”贴近月球表面做匀速圆周运动,其周期为T。“嫦娥1号”在月球上着陆后,自动机器人用测力计测得质量为m的仪器重力为P。已知引力常量为G,由以上数据可以求出的量有(       )

A.月球的半径

B.月球的质量

C.月球表面的重力加速度

D.月球绕地球做匀速圆周运动的向心加速度

答案

ABC

题目分析:A、由可以求出月球的半径;正确

B、由可以求出月球的质量;正确

C、由P=mg可以求出月球表面的重力加速度;正确

D、没有给出月球与地球间的关系,所以不能求出月球绕地球做匀速圆周运动的向心加速度;错误

故选ABC

点评:中等难度。把卫星的运动看成匀速圆周运动,万有引力提供向心力,通过测卫星的周期T、轨道半径r,则可推导出天体质量及密度,但只能求中心天体的质量和密度;若卫星在天体表面运行,只测出其周期即可。在天体表面,万有引力近似等于物体的重力。

阅读理解

阅读理解。

    When you are feeling unhappy or forget how great you are, these are six ways to make you feel

good about yourself.

    1) Look in the mirror and say to yourself, "I am a special person and there's no one in the world like

me. I can do anything!" It may not sound so good, but it really works!

    2) Do something nice for someone. Helping others always makes you feel good.

    3) Smile! Be friendly to people you meet. Look for the good things in your friends and family.

    4) Learn something new! Have you always wanted to decorate your own room or learn how to

swim? Go for it! New challenges (挑战) are fun and give you a sense of accomplishment when you

have finished.

    5) Read and start a diary. Turn off the TV and let your imagination (想象) fly! Write down your

thoughts,dreams or anything you want! Writing always helps to express your feelings.

    6) Stay with your family. We all need our family time. Talk with your Mum or Dad or maybe even

your cousin.

1. This passage may be taken from ______. [ ]

A. a science book

B. a story book

C. a magazine

D. school rules

2. According to the passage, when you are helping others, you will            . [ ]

A. be special

B. be sure

C. feel nice

D. be remembered

3. What do the underlined words in 4) "a sense of accomplishment" mean? [ ]

A. 成就感

B. 忧伤感

C. 挫折感

D. 信任感

4. Which of the following should you say "NO" to when you are unhappy? [ ]

A. You should always look for the good things of others.

B. Stay alone at home as much as possible.

C. Learn something new and go for it!

D. Keep a diary to express your feelings.

5. The best title (标题) for the passage is ______. [ ]

A. Do Your Best

B. Six Ways to Feel Good about Yourself

C. It's Never too Late to Learn

D. Always Smile to Your Life

单项选择题