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On a frictionless track, a trolley moves with a speed of with a mass of . A child whose mass is 20 kg runs on the trolley with a speed of from one end to other which is . The speed is relative to the trolley in the direction opposite to its motion. Find the final speed of the trolley and the distance the trolley moved from the time the child began to run.

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Mass is given as

Speed is given as

Mass of boy is given as

Initial momentum will be,

is final velocity of the trolley

Final velocity of boy can be calculated as,

According to law of conservation of energy, we have,

Initial momentum final momentum

Length

Distance moved by the trolley