Make your own balloon-powered car!

Here's how to make a car that's powered by balloons! Can you get your car to move? How far does it go?

The Experiment

Materials:

balloon
plastic straws
wooden skewers
cardboard
bottle caps, plastic drink lids, or anything else round (for wheels)
rubber band
tape

Try it out:

1. Put a balloon on one end of a straw and attach it by wrapping a rubber band around it:
2. cut out a cardboard rectangle (you can experiment with other shapes too). Tape a skewer on each end of the cardboard:
   
3. Poke holes in the bottlecaps or plastic lids and put them on each end of the skewers. You might have to use tape or rubber bands to keep the wheels from flying off. Make sure the wheels can spin!
4. Flip the cardboard so that the skewers and wheels are on the bottom.Tape the balloon and straw on the top of cardboard so that the straw is sticking out towards you.
   
5. Blow into the straw and then let the car go. Does it move? Try different sizes of cardboard and wheels, different positions of the skewers, and different materials.

What's happening

There are a few laws in physics called Newton's Laws. One of these laws says that for every action, there's an equal and opposite reaction. That just means that when you push on something, it pushes back!

When you blow up the balloon and then let the car go, the air escape out of the back. This is a force going backwards. Because of Newton's Laws, there is an equal force that pushes the car forward. Since there are wheels, this causes the whole car to move forward.

If you had trouble getting your car to move, it might be because you can't get enough force pushing the car forward. Try blowing up the balloon more or experimenting with different materials or sizes.

If you thought this was cool...

This experiment is related to mechanical engineering. You can find out more here.
Some ideas from physics in this experiment include Newton's Laws and Conservation of Energy.