How to Make a Balloon Car That Works

Building balloon cars is a way to get students interested in physics.

Building balloon cars illustrates the principles of rocketry and Newton's equal-and-opposite force law, helping students develop an interest in science and physics. In a rocket, the engine expels gases, pushing the rocket into space. The balloon car expels air, pushing it in the opposite direction. Designing a balloon car poses simple mechanical challenges and offers research opportunities related to recreational science.

Things You'll Need

• Rectangular tissue box
• Scissors
• Pencil
• Ruler or tape measure
• 2 straws
• 2 short wooden skewer sticks
• Duct tape
• Hammer
• Nails
• 4 plastic 20-ounce bottle caps
• Balloon

Instructions

1. Remove the top of a rectangular tissue box with scissors, leaving the vertical walls intact. This shape assists with the aerodynamics of the car.

2. Punch two holes in the vertical long walls of the tissue box directly across from one another. Make the holes with a pencil one inch above the bottom of the box and 2 inches in from the end of the box.

3. Slide a straw through the holes to form an axle. Tape the straw to the interior of the box to hold it in place. Insert a wooden skewer into the straw.

4. Punch another two holes in the vertical walls of the tissue box directly across from one another. Make these holes 1 inch above the bottom of the box and 2 inches from the other end of the box.

5. Slide a straw through to form another axle and tape it in place the same way as the first axle. Insert a wooden skewer through the straw.

6. Find a large diameter nail and use it and a hammer to punch a hole in the center of four bottle caps. Press each skewer end through a hole in a cap and fix it in place with tape if needed. Repeat this step for each of the caps.

7. Blow up the balloon three or four times to stretch it. Slide the end of a medium-size balloon over a plastic straw and cut it with scissors so that only 1 inch protrudes from the balloon. Punch a hole with a pencil, in the rear of the car near the bottom of the box. Slide the straw through the hole. Secure the straw with tape and ensure that the balloon is contained inside the box.

8. Blow up the balloon through the straw. Once the balloon fills the car, pinch the straw closed. Set the car on the ground and release the straw. The air expelled from the balloon will propel the car forward.

References

• Connect Ed: How to Build a Balloon Race Car for a High School Student
• Boast: Building a Balloon Rocket Car
• Nasa Quest: How to Build a Rocket Car