Two billiard balls each of mass 0.05 kg moving in opposite directions with speed 6 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, m = 0.05 kg 
Initial velocity of the ball = 6 m/s 
Magnitude of the initial momentum of the ball, p₁ = 0.05 x 6
    = 0.3 kg m/s
After collision, the balls change their directions of motion without changing the magnitudes of their velocity.
Final momentum of each ball, p_f = - 0.3 kg m/s
Impulse imparted to each ball = p_f - p_i = -0.3 -0.3 = -0.6 kg m/s
The negative sign indicates that the impulses imparted to the balls are opposite in direction.