Q.
A body of mass 2 kg moves down the quadrant of a circle of radius 4 m. The velocity on reaching the lowest point is 8 ms-1. Work done against friction is (take g = 10m/s2 )
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a
78.4 J
b
64 J
c
16 J
d
zero
answer is C.
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Detailed Solution
According to work energy theorem, work done by all forces =ΔKEWgr+Wfr=ΔK.E=12mv2−0=12×2×64=64⇒Wfr=64−Wgr=64−mgR=64−80=−16JThus work done by body against friction = 16 J
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