# A good rotational motion question!

Disc A has a mass of 4 kg and a radius $$r=75$$ mm ,it is at rest when it is placed in contact with the belt, which moves at a constant speed $$v=18$$ ms$$^{-1}$$ . Knowing that coefficient of kinetic friction is $$u_{k}=$$0.25 between the disc and the belt , determine the number of revolutions executed by the disc before it reaches a constant angular velocity Assume that the normal reaction by the belt on the disc is equal to weight of the disc.

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