Read about Galileo's famous Leaning Tower of Pisa accelerating objects experiment using school library books, articles, journals and Internet resources on academic websites. Use the plentiful information you are able to find on Galileo's experiment to form the basis for your project, which you can carry out either in or outdoors using a stepladder, a thick rubber sheet, a bowling ball and a friend or classmate with a stopwatch. You may also set up a tripod and video camera to film your experiment so you can watch it again later and time the falling of objects.
Write an hypothesis for your bowling ball and gravity experiment based upon your reading about Galileo's Experiment. Write your hypothesis clearly and succinctly in a log book, within which you should track all of your experiment activities; this helps you recall your experiment when it comes to preparing your science fair project. An example hypothesis for a bowling ball and gravity experiment could be that a bowling ball and a basketball would both hit the rubber sheet at the same time when dropped from the same height, even though they have different weights.
The ability to demonstrate your attention to health and safety during an experiment adds a strength and depth to your school science fair project. Prove that you followed health and safety guidelines during your bowling ball gravity experiment by laying flat a thick rubber sheet, for example, to protect both the bowling ball and the ground. Furthermore, establish a procedure for dropping any objects from a stepladder, such as shouting "clear" and looking for any people that may disrupt the experiment before dropping objects.
Carry out your experiment procedure by dropping different items from the stepladder to assess the effects of gravity. When assessing a bowling ball you need to find another ball that is roughly the same size, such as a basketball. Climb the stepladder to a set height, such as the ladder's third step and position your arms at the same position for all experiments. Ensure that you drop the bowling ball and basketball in the same way and from the same height to ensure your test is fair, and get a volunteer to observe the rubber sheet to see which ball strikes it first. Alternatively, watch your video to see which of the two objects hits the rubber sheet first.