Question

a man of mass 85kg stands on a lift of mass 30kg. when he pulls on the rope he exerts a force of 400N on the floor of the lift. calculate acceleration of the lift.

Answer 1

When the man pulls the rope with a force F = 400 N, let the upward acceleration of the lift be a. Also let T be the tension in the rope.

Now the equation of motion of the man is:

(mass of the man, m) × a = T + F - m g

85 a = T - 450 -------(1)

the equation of motion of the lift is:

30(mass of the lift) a = T - 400 - 30g = T - 700 -----------(2)

on solving both the equations, we get

a = 4.55 m/s²