This example deals with two objects ... kinetic energy is obviously not conserved. Is momentum conserved even though both cars stop? Yes, although there is no momentum after the collision ...

Here is a worked example. Two railway carriages collide and move off together. Carriage A has a mass of 12,000 kg and moves at 5 m/s before the collision. Carriage B has a mass of 8,000 kg and is ...