Suppose a train car moving down a track at 10 ms hits another train car that is not moving Explain how momentum is conserved after the collision?

Suppose a train car moving down a track at 10 ms hits another train car that is not moving Explain how momentum is conserved after the collision?
Suppose that 1st car is X-car and the 2nd car is Y-car.
Answer: After the collision, car X is no linger moving, but car Y is moving.