Energy Change During a Hip Check. Ice-hockey star Wayne Gretzky is skating at 13.0 m/s toward a defender, who in turn is skating at 5.0 m/s toward Gretzky . Gretzky's weight is 756 N; that of the defender is 900 N. Immediately after the collision, Gretzky is moving at 1.5 m/s in his original direction. You can ignore external horizontal forces applied by the ice to the skaters during the collision.
Calculate the change in the combined kinetic energy of the two players.