已知两个力F1、F2的夹角为90°,它们的合力大小为10 N,合力与F1的夹角

已知两个力F1、F2的夹角为90°,它们的合力大小为10 N,合力与F1的夹角为60°,那么F1的大小为(    )

A.5 N          B.5 N         C.10 N          D.5 N

答案

解析:如下图,|F1|=10cos60°=5 N.

答案

:B

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