Purpose:
To observe action and reaction forces in a balloon rocket.
Materials:
- Balloons of different shapes
- Long piece of smooth string (5m) to act as a track for your rocket
- Drinking straw cut into 5cm lengths
- Sticky tape
- Scissors
- 2 chairs or 2 friends
- Thin card
Procedure:
1. Thread the string through the straw. Attach the string to the chairs making sure it is tight and level. Or you can ask your friends to hold the string at either end and pull it tight.
2. Blow up a balloon and hold it closed so the air does not escape - do not tie it shut. Attach the balloon to the straw with sticky tape.
3. Move your balloon rocket to one end of the string and let go. How far does your rocket travel?
4. Try the same experiment with different shaped balloons. Which shaped balloon makes the best rocket?
5. You can decorate your rocket using the card to make fins and a nose cone. Does this make your rocket any better?
This simple experiment demonstrates that when there is an action force, which is the air escaping the balloon, there is a reaction force, which is the movement of the balloon forward, in the opposite direction to the air.
