作用在刚体上的力F对通过O点的某一轴y的矩是<img src=https://huaweicloudobs.ahjxjy.cn/6042BB8356C840BDC9C4BF7FD8B1F9CC.png title=QQ截图20190715141952.png alt=QQ截图20190715141952.png/>

【单选题】【消耗次数：1】

① 一个通过O点的固定矢量；

② 一个纯数量；

③ 一个自由矢量；

④ 一个滑动矢量。

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