# How to Make a Balloon Powered Car

Instructor: Amanda Robb
In this engineering project, you'll be designing a balloon powered car. Here, you'll learn about how Newton's third law can be applied to design propulsion vehicles like our car or a rocket.

## Introduction

 Goal: To create a balloon powered car that travels the farthest Age: Middle school and up Safety concerns: You'll be using scissors to poke holes in a bottle. Get an adult to help. Time: 1 hour

What makes a car move forward? What about a rocket? How does something so massive get in motion? Although fuel, like gasoline, is probably your answer, there's some physics behind why burning that fuel works. Newton's third law says that for every action there is an equal but opposite reaction. To review Newton's third law before we start, take a look at this lesson: Newton's Third Law of Motion: Examples of the Relationship Between Two Forces.

To understand how this applies to motion, let's look at the car example. When the fuel burns, it creates a force pushing backwards. The equal but opposite force pushes the car forwards. Today, we're going to create a model of this using a balloon and a bottle as the car and explain how Newton's third law applies.

## Materials

• 1 balloon
• 1 - 20 ounce plastic bottle (uncapped)
• Duct tape
• Scissors
• 1 straw
• 2 wooden skewers
• 4 plastic bottle caps
• 1 sponge
• Meter stick

## Steps

1. Start by attaching the balloon to the straw and sealing it with duct tape. It's important to get a good seal.

Safety Tip!! Get an adult to help you punch holes in the bottle; scissors can be sharp.

2. Punch two holes in the bottle. One 2'' from the top of the bottle and the other 2'' from the bottom of the bottle.

3. Repeat step 2 on the other side being careful that the holes line up.

4. Cut about 1/2'' of the bottom of the bottle off.

5. Poke a hole in the top of the bottle about 3'' from the top.

6. Cut the sponge into four small squares that will fit inside the bottle caps when compressed.

7. Insert each piece of sponge into the caps.

8. Slide each skewer through the holes on the bottles so you have two axles on your car.

9. Stick the skewers into the sponges inside the bottle caps to attach the wheels.

10. Let the balloon stay outside the bottle and insert the other end of the straw into the hole at the top of the bottle. Let the straw extend out of the bottom of the bottle.

11. Now it's time to test your car. Make sure you mark off your starting point so you can measure how far your car travels. Blow up the balloon and let it go.

12. Measure how far your car traveled. You can blow up the balloon larger or smaller and see how it affects the distance traveled.

## Troubleshooting

Your balloon must be thoroughly attached to the straw. Make sure there are no leaks in your seal. Also make sure there is enough room in the holes in the bottle for the skewers to rotate. The motion should be smooth because if the skewers get stuck, your car won't go very far.

## Discussion Questions

What happened when you released the air in the balloon?

What forces propelled the car forward?

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