Question

a boy of mass 60kg running at 3m/sec jumps onto a trolley of mass 140kg moving with a velocity of 1.5m/sec in the same direction what is their common velocity

Answer 1

Initial momentum of the system = momentum of the boy + momentum of the trolley = 60 × 3+ 140 × 1.5

=> ΔP 1 = 180 + 210 = 390 Ns

Final momentum of the system, ΔP 2 = mass of the boy and trolley × common velocity

=> ΔP 2 = (60+140)v = 200v

By law of conservation of momentum,

ΔP 1 = ΔP 2

=> 390 = 200v

=> v = 1.95 m/s

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