Use the force of the air to propel a vehicle!
(Adapted from Science Projects in Renewable Energy & Energy Efficiency
written by the National Renewable Energy Laboratory, published and
copyright 1991 by the American Solar Energy Society, and distributed by the
National Energy Foundation. )
- Balloons of different sizes
- Masking tape
- 25 feet of thin fishing line (mono-filament line)
- Plastic drinking straws (one for each balloon)
- Some heavy books
- A 25 foot tape measure
- A pad of paper and pencil for writing measurements and
- Blow up each balloon, holding the end closed with your fingers so it
stays full, and have someone else tape a straw to the middle of the
balloons. Let the air back out of the balloons.
- Take the piece of fishing line and stretch it tight between the back of
two chairs spaced about 20 feet apart. Leave one end with a bow knot so
that you can untie it easily.
- Put some heavy books on the seats of the chairs to keep them from
- Untie the fishing line and push the line through one of the straws with
the front of the balloon facing and bring the balloon and straw back to
the other end (the starting line). Retie the string to the chair so the
fishing line is tight.
- Blow up the balloon as much as you can. Pinch off the end. Then let go
of the balloon. Measure how far it went along the fishing line.
Try another balloon of different sizes, or try the same balloon blowing
it 1/2 way full or 1/4 of the way full. Measure how far the balloon
- Write down each of the balloons type (round, long, small, large) and
how much you blew it up (full, 1/2 way, 1/4 full, just a little) and how
far each of the balloons travelled.
A law of physics says for every action, there is an equal and opposite
reaction. The force of the air escaping from the balloon and pushing out
the end forced the balloon to travel forward. This is the same principle
used in rockets. Yet, instead of air...the rockets use rocket fuel.
The air you blew into the balloon became stored energy. When you released
the balloon's end, the stored energy became mechanical energy moving the
Rather than flying all around the room, the straw and the fishing line kept
the balloon travelling in a straight line. What balloons worked best: the
long skinny ones or the round ones? What happened when you blew up the
balloon only half way or 1/4 of the way?
Do you think air can be used for moving a car? What about moving an
astronaut in space? Can you think of other things that compressed air can
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