Question

if uk is the coefficient of friction between block and surface then the net work done is​

Answer 1

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A block sliding on plank friction will act positive to velocity of block, work done by by friction on block will be negative.

Reaction pairs of friction will act on plank in forward direction so in friction of displacement, plank friction will do negative work on it.

when block reaches other end, both block and plank will move with common velocity.

(M+m)Vc =mV0

Vc = Mv0/ M+m

Loss in KE = ½ mV0² − ½ (M+m) (mV0 / M+m )²

This loss in KE is work against friction So, total work by friction is negative.

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