A man weighing 60 kg is standing on a trolley weighing 240 kg . The trolley is resting on frictionless horizontal rails. If the man starts walking on the trolley with a velocity of 1 m s - 1 , then af

Question

A man weighing 60 kg is standing on a trolley weighing 240 kg . The trolley is resting on frictionless horizontal rails. If the man starts walking on the trolley with a velocity of 1 m s - 1 , then after 4 s , his displacement relative to the ground is

TestHub · Accepted Answer

The trolley shall move backwards to conserve momentum. The backward momentum would be shared by both the trolley and the man.

Applying conservation of momentum,

$60 \times 1 = (240 + 60) v$ or $60 = 300 v$

or $v = \frac{60}{300} = \frac{1}{5} m s^{- 1} = 0.2 m s^{- 1}$

Speed of man w.r.t. ground,

$= (1 - 0.2) m s^{- 1} = 0.8 m s^{- 1}$

Displacement of man $= 0.8 \times 4 m = 3.2 m$

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