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A disc of radius R moves by rolling without slipping on a level surface with speed v0. Let A be a point on the rim of the disc. The acceleration of point A is

1. constant in magnitude as well as direction
2. constant in direction
3. constant in magnitude
4. cannot be determined

Correct answer: constant in magnitude

Solution

For rolling without slipping with the centre moving at constant v0, any rim point has only centripetal acceleration toward the centre of magnitude omega^2 R = v0^2/R. This magnitude is constant, but the direction continuously points from the rim point to the centre and so rotates. Thus the acceleration is constant in magnitude only.

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