Two carts are moving toward each other and undergo perfect inelastic condition. One Cart is 100g, moving 20m/s and the other one is 140g?

Question

Two carts are moving toward each other and undergo perfect inelastic condition. One Cart is 100g, moving 20m/s and the other one is 140g and moving with 50m/s. What will be the final velocity of the two carts after collision? 

Answer 1

Lets consider first cart moving towards east, while second cart moving towards west

By conservation of momentum

m₁u₁ + m₂u₂ = (m₁+m₂)v

v = (m₁u₁ + m₂u₂)/(m₁+m₂)

v = [(0.100 kg)(20 m/s) + (0.140 kg)(-50 m/s)]/(0.100 kg + 0.140 kg)

v ≈ -20.8 m/s

Together they move at 20.8 m/s in the same direction as the second cart was originally moving