1. Find a broom or any stick.
2. Spread your hands as far apart as you can along the broom.
3. Slowly slide you fingers together at the same speed. You will find that the finger close to the broom head doesn't move much compared to other finger.
4. Once you get you fingers together you have found the broom's [b]center of gravity[/b].
5. You balance the whole broom using one finger on that point.
6. [b]Try it again[/b], but only move one finger at a time. However, you will find your fingers touched at the broom's center of gravity again (no matter which finger you are moving! ;D ).
This applet show you the phyisc for this fun activity.
Virtual Physics laboratory Original URL
Fu-Kwun Hwang, Dept. Of Physics, National Taiwan Normal University.