Balloon-Powered Vehicles

Balloons are super fun to play with. Almost every kid has blown up a balloon, let it go, and giggled as it chaotically flies to the ground. Though this is a common experience for kids, rarely have they discussed it in terms of the science behind it (when the air rushes to escape the balloon it causes thrust and propulsion similar to a rocket). When you attach the balloon to something that can attempt to control it’s path and that is when you can begin to see the true power and energy of the simple air that they put into the balloon (watch this video that compares balloons and rockets for more info).

Using the simple power of the balloon, you can easily construct a moving vehicle using simple machine wheel and axles. For background on this, please read our previous post about ways to introduce the idea of simple machines and how you can “upcycle” everyday materials you already have access to. Combining the power of the balloon and the movement of the wheel and axles, you can turn almost anything into a moving vehicle (i.e. small boxes, plastic soda bottles, berry cartons, etc.). We like to begin with building a very basic balloon-powered car to ensure that everyone successfully creates functioning wheel and axle combinations. Then we like to open up the challenge to allow them to choose any recyclable materials they want and build an open-ended balloon-powered car of their choice. The open-ended challenge provides a great opportunity to discuss design considerations and makes for very unique classroom drag races. Both activities are outlined below.

MAKE THE BASIC BALLOON-POWERED CAR

Gather Materials:

  • Balloons
  • Cardboard (you will need 3″x6″ for each base and reserve scraps for the wheels)
  • Tape (strong tape like Duct Tape works best)
  • Rulers
  • Pencils
  • Scissors (Xacto knives or box cutters optional)
  • Plastic drinking straws
  • Bamboo skewer sticks
  • Plastic soda bottle caps
  • Optional decorative elements (markers, paint, feathers, etc.)
  • Place tape on the floor to create a racetrack. Consider using a yard stick alongside to show distance for the students to compare.

Make It: (based on this Sick Science video tutorial)

  1. Create a cardboard base that is 3″x6″.
  2. Measure and cut two 3″ pieces of straw.
  3. Tape the 3″ straw pieces to the bottom of the 3″x6″ cardboard base. These will hold your axles.
  4. Cut off the end of one balloon.
  5. Place the balloon over the end of a (new) straw and tape it to create an airtight connection.
  6. Tape the straw to the top of the cardboard base. Be sure that you do not tape the balloon because it needs to expand and contract.
  7. Measure and cut two 4″ pieces of bamboo skewer. (Be careful as you cut them with scissors.) These are your axles.
  8. Place the 4″ bamboo skewer pieces inside the 3″ straw pieces on the bottom of the cardboard base.
  9. Use a plastic soda cap to trace and cut 4 circles onto scrap cardboard. These will be your wheels.
  10. Use the leftover bamboo skewer stick to carefully poke one hole in the center of each of your 4 cardboard wheels.
  11. Attach the cardboard wheels to the axles.
  12. “Fuel up” your racer by inflating your balloon. Carefully pinch the straw to hold the air until you are ready for your car to go.
  13. Place your balloon-powered car on the ground and let it go.
  14. Discuss:
    1. Is anyone’s car faster than the others? Why?
    2. How do the wheel and axles function to move the car?
    3. How far does it go? What could make it go farther?
    4. What type of path does it travel? What could make it go straighter?
    5. What happens if you change the size of the wheels?
    6. What happens if you change the chassis (cardboard base) by using a different material (i.e. a soda bottle) or change the angle of the chassis?
    7. What happens if you change the length of the exhaust (straw connected to balloon)? How does that impact the car’s thrust?

MAKE THE OPEN-ENDED BALLOON-POWERED CAR

Gather Materials:

  • Balloons
  • Tape, glue
  • Rulers
  • Pencils
  • Scissors (Xacto knives or box cutters optional)
  • Bamboo skewer sticks, toothpicks, and/or round wooden dowel craft sticks
  • Plastic drinking straws
  • Miscellaneous recyclable materials (plastic soda bottles and caps, yogurt cups, small boxes, empty toilet paper tubes, etc)
  • Optional decorative elements (markers, paint, feathers, etc.)

Make It:

  1. Encourage students to base their design on what they learned from the basic balloon-powered car above. Ask them to consider:
    1. How does weight play a role in speed? distance? path?
    2. How could you add more power? (more balloons, etc.)
    3. How could you design the car for increased speed? (drag racing)
    4. How could you design the car for increased distance? (“fuel” economy)
    5. How could you design the car for increased strength? (demolition derby)
  2. Allow students to design their own balloon-powered car using any materials available (recyclable options plus bamboo skewers, etc.). Encourage students to choose varied materials for their bases in order to have variety. You want students to strive for creating the fastest car but you can also have a variety of “rewards” for different features and abilities.

Activities:

  • Create race tracks and compare:
    • speed,
    • performance, and
    • durability.

Want to learn more? Check out these resources: