The aim of this simple science fair project is to demonstrate the concept of center of gravity with a simple experiment.
1. A meter ruler or cane.
2. Some clay.
1. Take the meter ruler and support it by two fingers at two ends.
2. Slide your fingers towards each other slowly without unbalancing the ruler. They will meet under the center of gravity of the ruler.
3. Attach some clay somewhere on the ruler.
4. Support the ruler again by two fingers and repeat the experiment. You will see that your fingers will meet somewhere close to the lump of clay.
The center of gravity of an object is the average location where the weight of the object acts. In this experiment when you start off, one finger will be further from the center of gravity than the other. This finger will find it easier to slide across the ruler than the other as it is holding less weight. Hence when you slide two fingers towards each other, the one which is further from the center moves faster and the fingers automatically meet at the center of gravity. When you add a lump of clay to the ruler, the center of gravity shifts closer to the lump of clay and hence your fingers meet at a point closer to the lump of clay now.