Question

A railway wagon of mass ½ t moving with velocity of 10 km/h, is hit from behind by another railway wagon of mass 1*1/2 t moving at 15 km/h such that after the collision, they move together. Calculate the final velocity of the wagons.

Answer 1

Mass of 1st wagon=1/2 t=1/2 x 1000 kg=500 kg
Velocity of this wagon=10 km/h=2.8 m/s
Mass of 2nd wagon=3/2 t=1500 kg
It's velocity=15 km/h=4.17 m/s
According to the law of conservation of momentum,
Total momentum before collision = Total momentum after collision
(500 x 2.8) + (1500 x 4.17)=(500+1500) x v
1400+ 6255=2000 v
v=3.8 m/s
Thus, the final velocity of wagons is 3.8 m/s.