When you play billiards, can you predict the velocities of the billiard balls after a collision if you know the velocity of a moving ball before the collision? assume the velocity of the first ball before the collision is v1i. the velocity of the second ball before the collision is zero. the balls have the same mass. a. find the velocity of the first ball after the collision. assume that the collision is head-on and elastic and that rotational motion can be ignored. express your answer in terms of v1i. b. find the velocity of the second ball after collision in terms of other velocities. express your answer in terms of v1i.