Question

A boy of mass 60 kg running at 3 metre per second jumps on a trolley of mass 140 kg moving with a velocity of 1.5 metre per second in the same direction What is their common velocity

Answer 1

This is a question on momentum.

Initial momentum = Final momentum

Momentum = mass × Velocity

The initial momentum of the boy and the trolley is :

(60 × 3) + (140 × 1.5) = 390

Let the trolley together move at a velocity of V then the final momentum will be:

(140 + 60)V = 200V

390 = 200V

V = 390/200 = 1.95 m/s

Answer 2

Explanation:

(m1+m2)v=m1u1+m2u2. v=m1u1+m2u2/m1+m2

(60*3)+(140*1.5)/(60+140)

=1.95 m/s