A 220 lb running back is running along the sideline of the football field toward the goal line. The running back is 1.0 m from the sideline running at 8.0 m/s toward the goal. A 180 lb defender runs across the field toward the running back 2.0 m from the goal line. Just before the collision, both players leap into the air. The running back keeps his horizontal speed of 8.0 m/s. What must be the defender's horizontal speed in order to ensure the players cross out of bounds before crossing the goal line?
System: The running back and the defender, treated as point particles. External influences are negligible compared to the internal forces of the collision, and so are neglected.
Model: Momentum and Impulse.
Approach: