Gravity Experiments, Reducing Gravity, and Amplifying Gravity

Gravity Experiments, Reducing Gravity, and Amplifying Gravity

Center of Gravity

Purpose: To determine how the height of the center of gravity of an object affects its ability its mechanical stability (falling over).


Two empty 2-liter soda bottles with lids

Tap water


Fill one bottle to overflowing with water, and fill the other bottle about one-fourth full. Seal the bottles with their caps.

Stand the bottles side by side on a table.

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.

Predict: How will the amount of water affect its center of gravity and stability? Which bottle will likely fall first?

True or False? short person is less likely to fall than a tall person? Why?

Try this: Does the length of your feet affect how far you can lean forward without falling?


The center of gravity of an object 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 the 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.

Why? An object is in a state of mechanical stability when it falls back to its original position when tilted slightly. 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.

True or False? True! The height of a person doesn't affect whether or not they might trip, but it does affect the mechanical stability of the person. Generally, shorter people have a lower center of gravity and greater mechanical stability than a tall person.