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问题 填空题

在太阳系中，有八大行星绕着太阳运行，按着距太阳的距离排列，由近及远依次是：水星、金星、地球、火星、木星、土星、天王星、海王星，如果把这些行星的运动近似为匀速圆周运动，那么它们绕太阳运行一周所用的时间最长的是______，运行角速度最大的是______．

答案

设太阳的质量为M，行星的质量为m，轨道半径为R，运动周期为T，角速度为ω．

由牛顿第二定律得

    G

Mm
R2
=m
4π2R
T2
    得T=2π
R3
GM
ω=
2π
T
=
GM
R3

则行星的轨道半径越大，周期越大；轨道半径越小，角速度越大．所以海王星轨道R最大，周期最大．水星轨道半径最小，角速度最大．

故答案为：海王星；水星

问答题 简答题

柴油机试验后应如何进行检查？
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问答题

Task 5
Conversation: The following are two business letters. After reading them, you should give brief answers to the 5 questions (No. 56 through No. 60) that follow. The answers should be no more than 3 words. They should be written after the corresponding numbers on the Answer Sheet.

Letter One

Dear Sirs,
On 5th October I bought one of your expensive "Apollo" fountain pens from Julian’s, a big department store of this town. Unfortunately I have been unable to use the pen because it leaks and fails to write without making blots. I am very disappointed with my purchase.
On the advice of Julian’s manager I am returning the pen to you and enclose it with this letter for correction of the fault.
Please arrange for the pen to be fixed or replace it with a new one and send it to me as soon as possible.
Letter Two

Dear Sirs,
Thank you for your letter of 9th October enlosing the defective "Apollo" fountain pen, received today. We very much regret that the pen you bought has given you trouble.
Normally each of our pens is individually examined before being passed into store and it is hard to understand why this one escaped examination. We have passed your pen to our quality control department for inspection and report. Meanwhile, we are arranging to replace your pen with a new one.
We extend our apologies for the inconvenience this matter has caused you, but are confident that the replacement pen you will be receiving will prove satisfactory.

When was the Letter One writtenIt was written ______.
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