A (trolley + child) of total mass 200 kg is moving with a uniform speed of 36 km/h on a frictionless track. The child of mass 20 kg starts running on the trolley from one end to the other (10 m away) with a speed of 10 `ms^(–1)` relative to the trolley in the direction of the trolley's motion and jumps out of the trolley with the same relative velocity. What is the final speed of the trolley? How much has the trolley moved from the time the child begins to run?

Explanation

The child gives an impulse to the trolley at the start and then runs with a constant relative velocity of `4 ms^(-1)` with respect to the trolley.s new velocity. Apply momentum conservation for an observer outside. `10.36 ms^(-1), 25.9m`.