Concepts

Circular motion, instantaneous velocity of an object moving in a circle.

Overview

Swing the ball on the string to show circular motion. Release the ball to show the instantaneous velocity of the ball.

Details

Equipment

• [1] Ball on a string

Important Notes

• When demonstrating circular motion, swing the ball in a vertical path to increase visibility.
• When demonstrating the instantaneous velocity of an object moving in a circle, swing the ball in a horizontal path to avoid complications due to gravity (the ball will travel along a parabolic path when released during a vertical swing whereas it will travel along a roughly horizontal path when released during a horizontal swing).
• It is easy to hit a student when releasing the ball. Practice this demonstration in advance.

Script

To show circular motion:

1. Hold onto the end of the string.
2. Swing the ball in a vertical path.

To show the instantaneous velocity of an object moving in a circle:

1. Hold onto the end of the string.
2. Swing the ball in a horizontal path.
3. Release the string. The ball will continue along a roughly horizontal path (the ball will fall, but it is not as obvious as when the ball is released in a vertical swing).

Additional Resources