题干

如图为“高分一号”卫星与北斗导航系统中的“G1”卫星,在空中某一平面内绕地心O做匀速圆周运动的示意图.已知卫星“G1”的轨道半径为r,地球表面的重力加速度为g,地球半径为R,万有引力常量为G.则(   )

A:“高分一号”的加速度大于卫星“G1”的加速度

B:“高分一号”的运行速度大于第一宇宙速度

C:地球的质量为 gr2G

D:卫星“G1”的周期为 2πrRrG

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答案(点此获取答案解析)

A,D

同类题1

阅读下面短文, 完成表格中所缺的信息,每空一词。

    Travelling is a very good activity. When you get tired of your work or study, and when you have free time, you can go to a beautiful place to enjoy the beauty(美丽) of nature(大自然) or other cities. You can take in fresh air, meet different people and make friends with them. It's good for your health to do so.

    But sometimes, travelling is not an enjoyable thing. For example, the weather can be changeable. There may be rain when you travel. You may catch a cold or be ill while travelling. The worst(最糟糕的) thing is that the thieves may steal(偷) your money. All these may happen to a traveler.

    When you go on a trip, you must get everything ready. Firstly, you must have clear information about the weather. Secondly, ask a friend to go with you so that you can help each other. Thirdly, you must be careful everywhere and try not to cause accidents(引起事故). If you do these, you will enjoy your travel.

Title (标题):____

Advantages

(优点)

You can enjoy the____views (景色) of the nature.

There will be a lot of____air around you.

It can make you ____.

Disadvantages

 (缺点)

Sometimes it ____when you travel. It will make

the road wet and slip(湿滑).

You may get ____when travelling.

The worst thing is that you may lose(丢失) some ____.

Advice

(建议)

 ____, you should know about the weather clearly. Second, you can ____someone to go with you.

Third, do everything carefully. ____ cause any accidents.