Question

A boy of mass 50kg running at 5m/s jumps on to a 20 kg trolley travelling in the same direction t 1.5 m/s. What is the common velocity? ​

Answer 1

Answer:

v =50+20/ 5+1.5

70/6.5.

=0.982

Answer 2

Answer:

4 m/s

Explanation:

Let positive direction be the initial direction of travelling of boy and trolley

We know, Linear Momentum=Mass×Velocity

Initial Linear Momentum for Boy=50kg×5m/s =250kgm/s

Initial Linear Momentum for trolley=20kg × 1.5m/s =30kgm/s

Total Initial Linear Momentum=250+30=280kgm/s

As no external force is acting on the system, so Linear Momentum will remain conserved.

The boy and trolley will move in same direction with same velocity.

Let common velocity=v

Final mass of system=50+20=70kg

Final linear Momentum of system=70kg×v

Initial Linear Momentum = Final Linear Momentum

280kgm/s=70kg×v

So v=4 m/s

Common Velocity=4m/s in the initial direction.