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 $, then the frictional resistance offered by the body is
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(d) $R = m(g - a)$ for downward motion of lift
If $a = g$ then $R = 0$ $\therefore \;\;F = \mu \;R = 0$
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