A man weighing 60 kg is in a lift that descends with an acceleration of 4 cmcdot s^(-2). What force will the man exert on the floor of the lift?

A man weighing 60 kg is in a lift that descends with an acceleration o

1.	A man weighing 60 kg is in a lift that descends with an acceleration of 4 cmcdot s^(-2). What force will the man exert on the floor of the lift?
Answer» Solution :If the lift descends with an acceleration a, and if the reaction force exerted by the lift on the MAN in the upward direction is R, then mg - R = ma `therefore` Force exerted by the man on the lift.s floor, R= mg - ma [ 4 cm`cdot s^(-2)` ] = 60(9.8 - 0.04) = 585.6 N If the lift ascends with the same acceleration, then reaction force on the man is, R.= mg + ma[ 4 cm`cdot s^(-2) = 0.04 m cdot s^(-2)` ] = 60(9.8 + 0.04) = 590.4 N When the acceleration of the lift, while descending, is a = g, then from equation (1) , we get, R = mg - mg = 0, for this zero reaction force, the man feels weightless. So, for a lift falling freely with an acceleration g, the man inside it will feel no weight.