A boy of mass m is standing on a toboggan of mass m which is moving with constant velocity vi over the surface of a frozen lake. the boy then runs along the toboggan in the direction opposite to vi and acquires a speed v relative to the toboggan as the toboggan in the direction opposite to Vi and acquires a speed v relative to the toboggan as he jumps off the rear of the toboggan. What is the final speed of the toboggan relative to the ice? Solution : Vf =Vi +mv/(M+m)