circular motion

用戶85377

2010-04-28 3:02 am

For 1,2, there is friction at first. Along the turnable is set to rotate and the angular speed is gradually increased, what would be the change of friction?

1. In circular motion, there is no friction acting on the block. What is the condition? Explain.

2. In circular motion, the block can remain at rest relative to the turnable. What is the condition? Explain.

回答 (1)

天同

2010-04-28 4:02 am

✔ 最佳答案

Your question is not clear. I suppose there is a block rested on a stationary turntable. The turntable then starts to rotate. The rotational speed gradually increases.

1. If there is no friction at all, the block would not go with the rotation of the turntable.

2. If friction is present, then frictional force could provide the necessary centripetal acceleration to the block. The block would then rotate together with the turntable.

When the rotational speed is gradually increased, the required friction also increases accordingly. But when the rotation is up to a speed such that limited friction is reached, further increase of speed would lead to sliding of the block away from the rotational centre, because there is not strong enough frictional force to provide the necessary increased centripetal force.

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