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Balloon Powered Car

Learn how air pressure powers a homemade racer across the floor. We’ll give you step-by-step instructions on how you can build your own race car and then use air pressure to race it across a surface.

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Key Concepts

  • Kinetic energy
  • Potential energy
  • Conservation of energy
  • Newton’s Laws of Motion

Instructions

        1. Cut one of the straws in half. 
        2. Tape both pieces of the straw
          to one side of the water bottle. 
        3. Cut the wooden skewer in half and push each piece through one of the straws (axles). 
        4. Have an adult help to make a hole directly in the center of each plastic bottle cap. 
        5. Press each bottle cap onto the ends of the wooden skewers.
          brainstem balloon powered car

          brainstem balloon powered car

           

           

           

        6. Put your car down on a flat surface.
          Test if the car rolls easily and coasts for a bit before stopping.
        7. Tape the neck of the balloon around one end of the other straw.
        8. Cut a small hole in the top of the water bottle, just big enough to push the straw through. 
        9. Push the free end of the straw through the hole and out the mouth of the bottle.
        10. Use tape to secure the straw to the bottle.
        11. Blow through the straw to inflate the balloon, then put your finger over the tip of the straw to trap the air.
        12. Put the car down on a flat surface and release your finger.
        brainstem balloon powered car

        brainstem balloon powered car

           

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    Questions you may ask

    1. What happens when you release your finger? 
    2. What adjustments you can do to make the car go farther. 
    3. What happens if you inflate the balloon more? 
    4. What happens if you adjust the direction the straw is aimed? 
    5. Does it work best if the straw is aimed straight back?

    Materials

    • Empty bottle
    • 4 bottle tops (the ones from fruit or baby squeezers)
    • 1 small Wooden skewer
    • 2 straws (one needs to have the flexible head)
    • Duct tape
    • Balloon
    • Nail, hammer, knife, scissors