The mass of the child is 26.0 kg and that of the boat is 55.0 kg. A ball moving with a speed of 17 m/s strikes an identical ball that is initially at rest. After the collision, the incoming ball has been deviated by 45o from its original direction, and the struck ball moves off at 30o from its original direction. What are the speeds of the two balls after the collision? A 0.450-kg hockey puck, moving east with a speed of 4.20 m/s, has a head-on collision with a 0.900-kg puck initially at rest. Assuming a perfectly elastic collision, what will be the speed and direction of each object after the collision. A ball of mass m makes a head-on-elastic collision with a second ball (at rest) and rebounds with a speed equal to one-fourth its original speed. What is the mass of the second ball?