Question

A boy of mass 70 kg running at 3 m/s jumps on a stationary trolley of mass 20 kg. If both start moving together then find the common velocity?

Answer 1

Explanation:

M1V1=M2V2

70×3=90×v

v=210/90

v=7/3

Answer 2

Answer:

Explanation:

m1 = 70kg

u1 = 3m/s

m2 = 20 kg

u2 = 0

v1 = v2 = v (because both boy and trolley will move with same vel.)

law of conservation of momentum

m1u1 + m2u2 = m1v + m2v

70*3 + 20*0 = (m1+m2)v

210 = (70+20)v

v = 21/9

   = 7/3m/s

  = 2.33 m/s(approx.)