题目内容

平面一般力系的平衡条件是()

A. 主矢为0,主矩为0
B. 主矢不为0,主矩为0
C. 主矢为0,主矩不为0
D. 主矢不为0,主矩不为0

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1a. Light travels faster than..

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A. rest
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