问题 选择题

下列说法中正确的是(  )

A.物体静止时,一定不受力

B.物体运动状态改变时,一定受到力

C.物体受力时,它的运动状态一定改变

D.物体不受力时,一定处于静止状态

答案

A、物体静止时受平衡力作用,如静止桌面上的课本,所受的支持力和重力为一对平衡力,故A错误;

B、因为力是改变物体运动状态的原因,因此物体运动状态改变,一定受力的作用,故B正确;

C、物体受平衡力时,运动状态不变,故C错误;

D、物体不受力时,物体处于静止状态或匀速直线运动状态,故D错误.

故选B.

完形填空
完形填空。
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a.m. and gets home at 5:00 p.m. Tom and Tim are his twin sons.   7   are not in our school. They are in No.1
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