a train is travelling up an a 3.73 degrees incline at a speed of 3.25m/s when the last car breaks free and begins to coast without friction.

How long does it take for the last car to come to rest momentarily?

Do you have the mass of the car? if yes it is simple then, you can use the equation: V=at + V0 You know that V0 = 3.25m/s and V is equal to zero (it stops at the end) so you only need to find the acceleration a (which must be negative) using Newton's 2nd law: - mgsinα=ma then a=-gsinα (and α=3.73