PRACTICE Problems 13. Two freight cars, each with a mass of 3.0X105 kg, collide and stick together. One was initially moving at 2.2 m/s, and the other was at rest. What is their final speed? 14. A 0.105-kg hockey puck moving at 24 m/s is caught and held by a 75-kg goalie at rest. With what speed does the goalie slide on the ice? 15. A 35.0-g bullet strikes a 5.0-kg stationary piece of lumber and embeds itself in the wood. The piece of lumber and bullet fly off together at 8.6 m/s. What was the original speed of the bullet