地球质量大约是月球质量的81倍，一个飞行器在地球与月球之间，当地球对它的引力和月球对它的引力大小相等时，该飞行器距地心的距离与距月心的距离之比为：
A．1：9
B．9：1
C．1：27
D．27：1
答案：B
题目分析：我们可设月球质量为M，那么地球质量就为81M．设飞行器距地心距离为
，飞行器距月心距离为
．由于地球对它的引力和月球对它的引力相等，根据万有引力定律得：
，解得：
故选B
点评：关键是抓住两者对飞行器的引力相等列式，基础题，比较简单
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