Two billiard balls each of mass 0.02 kg moving in opposite directions with speed 5 m s−1 collide and rebound with the same speed. What is the impulse imparted to each ball due to the other?

Mass of each ball = 0.02 kg Initial velocity of each ball = 5 m/s The magnitude of the initial momentum of each ball, pi = mass × velocity = 0.02 × 5 = 0.1 kg m/s After the collision, the balls change their directions of motion without changing the magnitudes of their velocity. Final momentum of each ball, pf = − 0.1 kg m/s Impulse imparted to each ball = Change in the momentum of the system = pf − pi = – 0.1 – 0.1 = – 0.2 kg m/s The negative sign indicates that the impulses imparted to the balls are opposite in direction.