Question

A boy of mass 50 kg running 5 m/s jumps on to a 20 kg trolley travelling in the same direction at

1.5 m/s. Find their common velocity.

Answer 1

According to law of conservation of momentum…

M1V1+M2V2= MV

50×5+20×1.5=(50+20)V

Where V is common velocity.

So,

250+30= 70×V

280/70=V

V= 4m/s.

Answer 2

Mass of boy = m1 = 50 kg

Mass of trolley = m2 = 20 kg

Initial velocity of boy = u1 = 5 ms-1

Initial velocity of trolley = u2 = 1.5 ms-1

Final velocity =

v = m1u1 + m2u2 \ m1 + m2

50 × 5 + 20 × 1.5 ÷ 50 + 20

= 4ms-1

HOPE IT HELPS YOU!!!