Did you know you can make and launch a water bottle rocket using just a plastic bottle, water, cork, needle adaptor and pump?
How do water bottle rockets work?
As you pump air into the bottle the pressure inside the bottle builds up until the force of the air pushing on the water is enough to force the cork out of the end of the bottle. The water rushes out of the bottle in one direction whilst the bottle pushes back in the other. This results in the bottle shooting upwards.
How to make a Bottle Rocket
What you need
- an empty plastic bottle
- cardboard made into a cone and 4 fins
- a cork
- a pump with a needle adaptor
You can buy a kit with the parts apart from the pump and the bottle – please check the contents before buying
Instructions – how to make a bottle rocket
- Push the needle adaptor of the pump through the cork, it needs to go all the way through so you might have to trim the cork a little bit.
- Decorate the bottle with the cone and fins.
- Fill the bottle one quarter full of water and push the cork in tightly.
- Take the bottle outside and connect the pump to the needle adaptor. Ours wouldn’t stand up on the fins so we rested it on a box, but if you make some strong fins it should stand up by itself.
- Pump air into the bottle, making sure all spectators stand back, the bottle will lift off with force after a few seconds.
Please make sure an adult is around as the rocket takes off very suddenly and forcefully as you can see in this video clip. Do not approach the rocket once you have started pumping even if it looks like nothing is happening.
Why does the water bottle rocket launch?
As you pump air into the bottle pressure builds up inside. If you keep pumping, the force of the air pushing on the water eventually becomes strong enough to force the cork out of the bottle allowing water to rush out in one direction while the the bottle pushes back in the other direction. This forces the rocket upwards.
Space rockets work in a similar way to the bottle, but instead of squirting water they burn fuel to make a powerful jet of hot gas. The force of the gas downwards pushes the rocket upwards. This is a great demonstration of Newton’s Third Law.
What is Newton’s Third Law?
Newton’s Third Law says:
‘for every action there is an equal and opposite reaction’
Who was Issac Newton?
Issac Newton was an English scientist most famous for his theory of gravity, but he also worked out three laws of motion to describe how objects move. You can find out more about the Three Laws of Motion in my book, This Is Rocket Science which has lots of activities to demonstrate all three laws based around rockets and space.
Find out how to make a rocket mouse
Make a film canister rocket
Try one of these other easy air pressure experiments, including making a fake lung, a barometer and a coin popper!
Can you show a friend how to make a bottle rocket?
Buy the book!
For more fun rocket science activities check out our new book This Is Rocket Science
Images taken from This Is Rocket Science