A train of mass M is travelling with a uniform velocity on a level line . The last carriage whose mass is m gets detached from the train . The driver of the train discovers it only after travelling a distance l and then he shuts off steam . Show that when both parts come to rest the distance between them is `((Ml)/(M - m))` . Assume resistance of motion to be uniform and proportional to mass and the pull of the engine to be a constant .