A solid sphere, a hollow sphere and a disc, all having same mass and radius, are placed at the top of an incline and released. The friction coefficients between the objects and the incline are same and not sufficient to allow pure rolling. Least time will be taken in reaching the bottom by

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the solid sphere

the hollow sphere

the disc

all will take same time

answer is D.

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Detailed Solution

Since point A is moving, kinetic friction will be present.

$f = μmgcosθ$

$ma = mgsinθ - μmgcosθ$

a is same for all the bodies,

$s = 0 + \frac{1}{2} {at}^{2} = \frac{1}{2} {at}^{2}$

where s is the length a body travels on an inclined plane. Thus for same s , all will take the same time.

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