Suppose two balls A and B of masses m and km are moving in the same direction with speedsandrespectively, whereand 0 We can find the coefficient of restitutionin terms ofandand use the expression for e to conditions onand Conservation of momentum gives (1) Ifis the coefficient of restitution between A and B, then(2) k*(2) – (1) gives Because e <=1, we must have We havehenceand