A ball of mass 0.206 kg with a velocity of 1.54 m/s meets a ball of mass 0.291 kg with a velocity of -0.396 m/s in a head-on, elastic collision. (a) Find their velocities after the collision. V1f = m/s V2f = m/s (b) Find the velocity of their center of mass before and after the collision. Vcm, before = m/s Vcm, after = m/s