The floor is smooth. Y and Z are in contact. The mass of the balls are m,m and 2m as stated. Assume all collision is elastic, what are the velocity of the three balls after all collisions?? Now, Y and Z are reversed in position. At the time of collision, what would happen for the three balls in a mathematical explanation?? If we view Y and Z as one object, then the two will experience same force but different velocity, in the equation, I just can't separate the different velocity out since Y and Z are treated as one!!!!! HELP!!!!