试题与答案

如图所示,质量为M劈体ABCD放在水平地面上,表面AB、AC均光滑,且AB∥CD

题型:选择题

题目:

如图所示,质量为M劈体ABCD放在水平地面上,表面AB、AC均光滑,且AB∥CD,BD⊥CD,AC与水平面成角θ。质量为m的物体(上表面为半球形)以水平速度v0冲上BA后沿AC面下滑,在整个运动的过程中,劈体M始终不动,P为固定的弧形光滑挡板,挡板与轨道间的宽度略大于半球形物体m的半径,不计转弯处的能量损失,则下列说法中正确的是

A.水平地面对劈体M的摩擦力始终为零

B.水平地面对劈体M的摩擦力先为零后向右 

C.劈体M对水平地面的压力大小始终为 (M+m)g

D.劈体M对水平地面的压力大小先等于(M+m)g,后小于(M+m)g

答案:

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参考答案:对

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陕西河南山西河北甘肃四川江苏安徽浙江江西福建广东湖北湖南云南
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