Question

A railway carriage of mass 20000kg moving with a speed of 25m/s hits a stationary carriage of same mass.After the collision the carriages get coupled and move together.what is their common velocity after collision

Answer 1

Initial velocity = 25 m/s

Mass of each railway carriage = 20000 kg

Initial momentum = 20000 × 25 + 20000 × 0

Initial momentum = 500000 kg m/s

Let the common velocity after collision be v.

Now,

Final momentum = (20000 + 20000) × v

Since, the forces during collisions are internal. Hence, the momentum of the system will be conserved.

Initial momentum = Final momentum

40000v = 500000

$v = \frac{500000}{40000}$

v = 12.5 m/s

Hence, the common velocity after collision is 12.5 m/s