various bouncing balls meter stick stopwatch . postal scale PROCEDURE: 1. Weigh one of the bouncing balls and determine its 2. Place a meter stick (vertically) on the ground. 3. From 1 meter, drop the ball, then accurately determine and record the height to which it returned. 4. Repeat four times, each time starting at the returned height of the previous trial. 5. Repeat steps 1 - 4 with two other types of balls