A block of mass 1kg slides down a curved track that is one quadrant of a circle of radius 1m. Speed of the block at the bottom is 2m/s. Work done by the frictional force on the block when it reaches at the bottom is:
A
8J
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B
−8J
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C
4J
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D
0J
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Solution
The correct option is A−8J Given, m=1kg, v=2m/s R=1m W=? From energy conservation, mgh+W=12mv2 W=12mv2−mgh =12×1(2)2−1×10=−8J.