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. )
What do you need?
- 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 observations
What to do?
- 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 tipping over.
- 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 travels.
- 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 traveled.
What you'll discover!
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 balloon.
Rather than flying all around the room, the straw and the fishing line kept the balloon traveling 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 do?