A ball of mass 2m slides along a frictionless track with speed u. Starting from a long distance away, it collides elastically with a stationary ball of mass m. (a) Calculate the final speeds of both balls (you may neglect any rotation of the balls). (b) If both balls were now positively electrically charged, describe qualitatively either how the results would change or why you would leave the results unaltered. [5] [2]