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问题 单项选择题

计算钻杆的最大安全静拉力，在采用拉力余量法时，拉力余量一般取（）KN。

A.100-300

B.200-400

C.200-500

D.300-500

答案

参考答案：C

阅读理解
阅读理解，填表。
     It's a fine Sunday morning. Ann and her mother are in a big bus. There are many people in it. Some
of them come from America, and some come from England and Canada. They are all their friends. They
are going to the Great Wall .      
    There are two Chinese in the bus. One is a woman. She is driving the bus. The other is a young man.
He speaks good English. He is now talking about the Great Wall. The other people are all listening to
him. They like the Great Wall. They want to see it very much.
The Place of
the vacation		The day of
the vacation		The 3_____ of
the vacation		The transportation (交通)
of  the vacation		The number of countries
in the bus the people
are from
1_____2_____sunny4_____5_____
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问答题

据报道，1992年7月，美国"阿特兰蒂斯"号航天飞机进行了一项卫星悬绳发电实验取得部分成功．航天飞机在地球赤道上空离地面约3400km处由东向西飞行，从航天飞机上向地心方向发射一颗卫星，携带一根长20km，电阻为800W的金属悬绳，使这根悬绳与地磁场垂直，做切割磁感线运动，假定这一范围内的地磁场是均匀的，磁感应强度约为，且认为悬绳上各点的切割速度都与航天飞机的速度相同，根据理论设计，通过电离层（由等离子体组成）的作用，悬绳可产生约3A的感应电流，试求：

（1）航天飞机相对于地面的大约速度?（地表面重力加速度为，地球半径为6400km）

（2）悬线中产生的感应电动势?

（3）悬线两端的电压?

（4）航天飞机绕地球运行一周悬线输出的电能?

 
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