Question

Two billiard balls each of mass 0.05 kg moving in opposite directions with speed 6 ms^–1 collide and rebound with the same speed. What is the impulse imparted to each ball due to the other?

Answer 1

Mass of each ball = 0.05 kg
Initial velocity of each ball = 6 m/s
Magnitude of the initial momentum of each ball, p_i = 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 = Change in the momentum of the system
= 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.