The tennis balls are kept in a box at constant temperature.At regular inercals,the umpire calls for new balls,because if we use the balls of low presure to limit the speed of rebound,it will be more easily to attack.The teacher asked we 2 do a experiment to considered it,i know we need to use the equation E=mgh,but when we do the experiment, how do i drop 2 balls from a different temperature,how do i draw the graph to include these things~? JUst need help ! ~ :)[/b]