- A balloon
- String (kite string and dental floss work well, but feel free to experiment!)
- A straw
- A Paperclip
- A friend to help!
When you blow up a balloon and let it go, it flies around the room out of control. But add a guidance system and you no longer have a crazy flying party favor. Now, it's a rocket!
So how do you make a guidance system? First, grab a straw. If it is a bendy straw, use scissors to cut off the bendy part so you only have the boring straight part left.
Next, we need some string. We like to use dental floss and kite string at the Science Center, but play and experiment. You might find something that works even better! Take one end of the string and feed it through the straw until it pops out of the other end. You may want to tie a paperclip onto the end to prevent the string from sliding back through the straw.
Now that our string is through the straw, grab your balloon and blow it up. Make sure to hold the end closed to no air escapes. Now, ask your friend to place the straw on the side of your balloon and attach the straw using tape.
Looks like we're nearly ready to launch! Make sure you stretch your string out and hold it tight on both ends. Take a look at your balloon to make sure you have it at the right end. You want the nozzle of your rocket (the part you used to blow up your balloon) pointing towards you so the balloon can fly away from you. Ready? 3...2...1...BLAST OFF!
So this is fun, but a balloon is nothing like a real rocket, right?
Actually, our balloon rocket works the same as a real rocket! The balloon rocket is a simple model for how rockets work and allows us to investigate Newton's Laws of Motion. In particular, Newton's Third Law of Motion which states: "For every action, there is an equal, but opposite reaction."
So what does this mean? Because we are talking rockets, let's think about what has to happen to make that rocket launch. Inside a big NASA rocket, a chemical reaction will occur to produce an expulsion of gas in the rocket engine. The gas expands and the rocket pushes it out. In return, the gas pushes on the rocket making it rise into the sky.
Our ballon is very similar. When we blow up our balloon the air inside pushes against the ballon and the balloon also pushes back against the air. When we let go, the balloon is able to squeeze all that air out, but the air also pushes back against the balloon causing to fly around the room, or if we've attached a guidance system, across the room in a straight line.
See how far you can make your balloon rocket fly and have fun experimenting!