57. A ball with a mass of 0.5 kg is traveling at 25 m/s and collides with a ball at rest that has a mass of 2 kg. After the collision, both balls are traveling 5 m/s in the same direction, Was momentum conserved? 58. Calculate the recoil (backward momentum) and velocity of a 4.0 kg rifle that fires a 20 g bullet that travels 1.0 m in 2.15x10 S. 59.