Blow up a balloon and then let it go. The force of the high-pressure air coming out of the neck makes the balloon rush aimlessly in all directions.
You can stop a balloon from flying recklessly out of control.
Make sure the balloon end with the button is not pointing towards your eyes.
1. Blow up the balloon and hold it by the neck. Do not tie a knot in the end.
2. Slip the button into the balloon’s neck so that the neck closes tightly about the button.
3. Let the balloon go. It will zoom off in a fairly direct line. It will take quite a long time for the balloon to empty, because the air inside cannot escape very quickly.
The stretched rubber of the balloon puts pressure on the air inside, but the button openings control the thrust of the rocket.