Center of Gravity: Tilted
 

	Fun Experiment to Try at Home!
		Purpose To determine how the height of the center of gravity of an object affects its mechanical stability, or falling over.   Materials - two empty 2-liter soda bottles with lids - tap water   Procedure 1.  Fill one bottle to overflowing with water, and fill the other bottle about one-fourth full. Seal the bottles with their lids. 2. Stand the bottles side by side on a table. 3. Tilt each bottle slightly, supporting the top of the bottle with your finger, and then release it. Does the bottle tip over, or does it return to a standing position? Continue increasing the amount of the tilt until one of the bottles falls over.   Sum It Up! An object is in a state of mechanical stability when it falls back to its original position when tilted sightly. The bottle with the lesser amount of water has a lower center of gravity. The lower the center of gravity, the greater the stability of the bottle, so it was able to be tilted farther without falling over.

A short person is less likely to fall than a tall person is.
 
The center of gravity of an object, including a person, is the point where the weight of the object appears to be concentrated. An object is stable when its center of gravity, the place where its weight seems to be concentrated, is located over its base.

The lower an object's center of gravity is compared to its height, the less likely it is to fall over. This ability to resist falling over is known as mechanical stability. The height of a person doesn't affect whether or not they might trip, but it does affect the mechanical stability of the person. This difference in the ability to resist falling over is due to the difference in the height of the center of gravity of each person. Generally, a shorter person has a lower center of gravity and thus greater mechanical stability than a tall person.

For more experiments about center of gravity, read "Janice VanCleave's Gravity." (New York: Wiley, 1993)