A lift is moving downwards with an acceleration equal to acceleration due to gravity. $A$ body of mass $M$ kept on the floor of the lift is pulled horizontally. If the coefficient of friction is $\mu $, if the lift is moving upwards with a uniform velocity, then the frictional resistance offered by the body is
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(b) When the lift is moving upward with constant velocity then, $R = mg$ $\therefore $ $F = \mu \;R = \mu \;mg$
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