Two balls collide head-on on a table. the first ball has a mass of 0.50 kg and an initial velocity of 12.0 m/s. the second ball has a mass of 0.75 kg and an initial velocity of -16.0 m/s. after the collision, the first ball travels at a velocity of -21.6 m/s. what is the velocity of the second ball after the collision? assume a perfectly elastic collision and no friction between the balls and the table. a. 6.4 m/s b. 11.3 m/s c. 17.8 m/s d. 21.6 m/s