## Introduction: Air Pressure Balloon Car

The concept behind the Balloon-Powered Car is pretty simple, but that doesn’t make it any less impressive. When you blow up the balloon, set your racer down, and let it go, escaping air from the balloon rushes out of the straw. This is your car’s propulsion system. As briefly mentioned in Step 8, the principle at work is Newton’s Third Law of Motion. This law states that for every action, there is an equal but opposite reaction. In the case of the Balloon-Powered Car, the action is the air rushing from the straw and pushing against the air behind the car. The reaction is the air behind the car pushing against the car with the same force causing the forward movement of the car.
The potential energy of the car is stored in the expanding elastic material of the balloon. As the balloon fills with air, it adds more potential or stored energy. As the air flows from the balloon, the energy changes to kinetic energy or the energy of motion. The moving Balloon-Powered Car is using kinetic energy. If you aim your car down a ramp from the top of the ramp, just lifting it up into position adds potential energy thanks to gravity. Upon release, the energy converts to kinetic and the car goes until there’s not enough to move it anymore. The first part of Step 8 was in fun but the points are correct. The rounder the wheels, the better. The parallel axles and wheels mean the car will travel in a straight line and not veer one way or the other and lose energy doing so. Centering the wheel on the axle means it rolls evenly without a wobble or an up and down movement which, you guessed it, eats up energy that could go to speed. Wow! There’s a lot packed into this simple design!

## Supplies

Material Required:

1) EVA Foam
2) Car Sticker Sheet
3) Straw
4) Wooden Skewers
5) Balloon
6) Glue
7) Tape

## Step 1: Gather All the Material

Air pressure powers a homemade racer across the floor.