Dancing Ping-Pong Ball (Funky Physics Experiments)

You will need:

1. Large wine glass with a
   long stem
2. Water
3. Ping-pong ball
4. Soap

Conduct this experiment as a neat party trick and surprise all your friends. Watch the ping-pong ball dance about. But do practise before-hand for the experiment.

INSTRUCTIONS

1. Take a large wine glass and dry it completely.
2. Wash your hands with soap and rinse thoroughly. Dry them completely.
3. Place a ping-pong ball in the wine glass and hold it steady by the stem of the glass with one hand.
4. Dip a finger of your free hand into water and rub the outside rim of the wine glass with your damp finger.
5. Once the rim makes a sound when you move your finger over it, tilt your glass sideways until the ping-pong ball inside is almost at the rim of the glass.
6. Rub your damp finger over the rim again when the glass is tilted and watch the ball dance.

RESULT

The ping-pong ball inside the glass starts dancing around because of the
natural frequency of glass when it vibrates. By rubbing your finger on the rim
of the glass, you are creating friction. Your finger sticks and slips over the rim
creating vibrations. These vibrations make the ping-pong ball jump around.