This activity will demonstrate that the air in our atmosphere has
mass which is attracted by the force of gravity.
Time requirement: 40 minutes as an activity, 15 minutes as a demonstration.
- 1 piece of dowel approximately 1 meter in length
- 2 balloons of the same size
- 1 drop of cooking oil
- 1 sharp pin
- Scotch tape
- Inflate the two balloons to approximately the same size. Tie the ends
of the balloons so that the air does not escape.
- Using the string, suspend the balloons from opposite ends of the dowel.
- With another piece of string attached near the middle of the dowel,
balance the dowel and the two balloons. A piece of tape at the balance
point will help prevent the string from slipping.
- When the dowel and balloons are balanced, suspend the apparatus from
some fixed point so that you are free to continue.
- Place a drop of oil on the outside of one of the balloons.
- Insert a pin through the oil into the balloon. The balloon should not
- Allow the balloon to deflate. The escaping air may cause the
apparatus to swing around.
- Describe what happened to the balanced dowel and balloons when one
of the balloons was deflated.
- Why did the dowel become unbalanced when all of the air in one of
the balloons escaped?
Last updated: March 17, 1998
Joe Twicken /