A railway truck of mass 4 x 10exp4 Kg moves at 3ms-1 towards a stationary truck of mass 2 x 10exp4 Kg. the trucks collide and join calculate the total momentum of the two before the collision. What is the total momentum of the two trucks after the collision? Find the speed at which the joined trucks move off after their collision. Compare the kinetic energy after the collision with that before the collision.

Momentum= mass x velocity

4 x 10exp4 x 3ms-1 = 120000 Kg ms-1

2 x 10exp4 x 0ms-1 = 0 Kg ms-1 ( by stationary I take it, it means 0 ?)

Total momentum = 120000 + 0 = 120000

Total momentum after collision is equal to total momentum before collision if you exclude all other factors?

Speed ?

KE = ½mv2

If this is all wrong, which I am pretty sure it is, can you please show your full working.

Thanks.