The physics of a person jumping onto a moving sled. A 75.0 kg person runs at 3.0 m/s and jumps onto a sled of mass 10.0 kg already moving in the same direction as the person at 2.0 m/s. a) What is the initial momentum of the sled-person system? b) What will the final momentum of the sled and the person be? c) What is the velocity of the sled and the person after the person jumps on the sled? The physics of a rifle and a bullet. An unconstrained rifle of mass 5.0 kg fires a 50.0 g bullet at a speed of 300.0 m/s with respect to the earth. a) What is the initial momentum of the rifle-bullet system? b) What is the recoil velocity of the rifle?