Six metal balls are suspended vertically so that when they hang down they are just physically touching each other in a straight line. If one ball is raised and let go from the right, one ball from the left will attain the same height and velocity as the ball from the right. Matematically prove that when two balls are raised from the right, that two balls from the left will move out and not only one metal balls with twice the velocity. (Assume the mass of each ball is one kg and the velocity of two raised balls equals 2 m/s.)