A man of mass 80 kg stands on a plank of mass 40 kg. The plank is lying on a smooth horizontal floor. Initially both are at rest. The man starts walking on the plank north and stops after moving a distance of 6 m in on the plank. Then

Options

A. The centre of mass of plank-man system remains stationary
B. The plank will slide to the north by a dsitance `4m`
C. The plank will slide to the south by a distance `4 m`
D. The plank will slide to the south by a distance `12 m`

Answer

(AC)

Explanation

Let x be the displacement of the plank.
Since CM of the system remains stationary
so `80 (6 - x) = 40 x rArr 12 - 2x = x rArr x = 4m`