A man weighing 60 kg is standing on a trolley weighing 240 kg. The trolley is resting on a frictionless horizonral rails. If the man starts walking on the trolley with a constant speed of `1 ms^(-1)` then after 4 second. The displacement of the man relative to the ground is :

Options

A. 4.2 m
B. 4.8 m
C. 3.2 m
D. 3 m

Answer

c

Explanation

According to law of conservation of momentum
`60 xx 1 = (60+ 240) upsilon` or `upsilon= 0.2 ms^(-1)`
Resultant speed of man `= (1 -0.2) = 0.8 ms^(-10)`
Now `S = ut = 0.8 xx 4 = 3.2 m`
(c) is the choice.