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Assertion : A sphere is placed in pure r...

Assertion : A sphere is placed in pure rolling condition over a rough inclined surface.Then, force of friction will act in downward direction

Reason : Angular acceleration (actually retardation) due to friction is anti-clockwise.

A

If both assertion and reason are correct and reason is the correct explanation of the assertion.

B

If both assertion and reason are correct but reason is not the correct explanation of assertion

C

If assertion is correct but reason is incorrect.

D

If assertion is incorrect but reason is correct

Text Solution

Verified by Experts

The correct Answer is:
C
On a real surface rolling sphere comes to rest after some time. Linear motion is retarded due to force of friction opposing it. But torque of friction becomes in the direction of angular velocity and cannot reduce it. So what happens is that surface and the body are little deformed so that normal reaction gets suitably shifted to apply torque opposite to angular velocity. Hence it.s not the torque of friction which opposes angular motion in this case rather it is torque of shifted normal reaction which reduces Angular speed. Eventually linear speed and angular speed both become zero simultaneously.
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