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## Homework Statement

A trolley of mass 200 kg moves with velocity of 10 m/s on a friction less track. A child of mass 20 kg runs on the trolley with a sped of 4 m/s relative to the trolley in the direction opposite to the trolley's motion and jumps out of the trolley. What is the final speed of the trolley?

## Homework Equations

La of conservation of momentum

## The Attempt at a Solution

My reference frame is moving with the velocity of the center of mass.

4*20=200*v

v=0.4

Therefore with respect to ground velocity of trolley=10.4 m/sec?

Is my answer correct?