试题与答案

如图2所示,一粗糙的环形细圆管,位于竖直平面内,环形的半径为R (比细管的直径大

题型:选择题

题目:

如图2所示,一粗糙的环形细圆管,位于竖直平面内,环形的半径为R (比细管的直径大得多),在圆管中有一个直径比细管内径略小些的小球(可视为质点),小球的质量为m,设某一时刻小球通过轨道的最低点时对管壁的压力为7 mg。此后小球便作圆周运动,经过半个圆周恰能通过最高点,则此过程中小球克服摩擦力所做的功可能是

A.mgR

B.mgR

C.2mgR

D.3mgR

答案:

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