Question

A wagon weighing 1000 kg is moving with a velocity 50 km/h on smooth horizontal rails. A mass of 250 kg isdropped into it. The velocity with which it moves now is

Answer 1

Given,
Mass of wagon , m1 = 1000kg
Velocity of wagon, V1= 50km/h
After dropping 250kg mass into wagon, mass of wagon m2= 1000+250= 1250 kg

Now Velocity of wagon,V2 = ?

By principle of conservation of momentum,m1V1 = m2V2
V2= (m1V1) / m2
= (1000 * 50) / 1250
= 40 km/h