This is one of my favorite demos to show how mass determines the inertia of an object. If you are going to do this demo in class, make sure you use fishing line that can handle the highest tension possible (great demo for tension as well) that you can buy at a local sporting goods store. I used goop adhesive to attach a paper clip to the golf ball, so that I could tie the fishing line to the golf ball. I tied both objects to the metal beams of the drop down ceiling in my classroom. Watch the video to see how the demo works.