Assertion : Work done by friction on a body sliding down an inclined plane is positive. Reason : Work done is greater than zero, if angle between force and displacement is acute or both are in same direction.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If assertion is false but reason is true.

Answer

D

Explanation

When a body slides down on inclined plane,
work done by friction is negative because it opposes the motion (`theta = 180^(@)` between force and displacement)
If `theta lt 90^(@)` then W = positive because `W = F.s. cos theta`