Schematic illustration of a pendulum.

Penny Balloon

How Can You Change the Center of Gravity of an Object?

 

Materials

  • two balloons
  • penny

Try This

  1. Stick the penny inside one balloon, blow up the balloon, and tie it off.
  2. Blow up the other balloon (with no penny) and tie it off.
  3. With an open palm, bounce the balloon with no penny in your hands 10 times.
  4. Bounce the balloon with the penny in your hands 10 times.

What's Going On?

The balloon with no penny doesn't shift that much because its center of gravity stays the same, so it is easy to bounce in your hand. The penny in the other balloon moves around, which shifts the balloon's center of gravity, making it much more unsteady and unpredictable.

Schematic illustration of throwing a balloon.