Build and Race a Balloon Powered Car

Balloon-powered cars are a fun way of demonstrating Newton’s Laws of Motion.


Balloon-Powered Car Challenge

Why not do this activity with others and challenge your friends to a race?

Print our handy poster for your own balloon car challenge.


View Poster
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Challenge poster.

There are several ways to make a balloon-powered car, so feel free to experiment and see if you can make one that travels further than ours!

Here are two different types to get you started:

#1 Bottle chassis car
#2 Card Chassis car

How it Works:

Balloon cars are a good demonstration of Newton’s Third Law of Motion, which states that every action has an equal and opposite reaction.

As you inflate your balloon, it becomes filled with air. This air exerts pressure on the inside of the balloon. As you release the balloon, the air rushes out (the action) and pushes against the air outside of the balloon, causing it to move forward in the opposite direction (the reaction).

Example #1

Making a bottle chassis balloon-powered car

Bottle chassis balloon powered car.

What you’ll need:

  • A plastic water bottle (small)
  • Bottle top lids (of equal size) x 4
  • Drinking straws x 4
  • Wooden barbeque skewers x 2
  • Sticky tape
  • Blu-tack
  • A ruler
  • Marker pen
  • A standard-sized balloon
  • Scissors
  • Pliers (for an adult to cut the skewers)
  • Hand drill (for an adult to make holes in the bottle tops)
Materials list.

It’s good to try out different types of wheels to see how they affect the car. Here are some material suggestions for alternative wheels:

  • Round beads
  • Empty thread spools
  • Plastic milk bottle tops
  • Sports drinks caps with the covers removed
  • Unwanted CD’s
Alternative wheels.

Step One – The chassis and wheels

SAFETY: This should be completed by a responsible adult or under supervision.

Place a piece of Blu-tack underneath the centre of the bottle top lid. Many bottle top lids already have a dimple to show the centre. If yours doesn’t, you will need to measure it to locate this.

Drill a hole through the centre of the four lids.

Carefully push a wooden BBQ skewer through the hole away from your hands.

Make holes for the axels.

Now cut one of the drinking straws into two equal lengths (these need to be wider than the bottle).

Then, thread the skewer through a drinking straw.

Next, add another bottle top lid onto the other end of the drinking straw away from your hands.

Snip the sharp end of the skewer off with a pair of pliers.

Making the axels.

Repeat step two with the other two lids.

Tape the drinking straws and wheels to one side of the bottle and remove the bottle lid.

Underside of bottle car.

Step Two – Attaching the balloon and racing your balloon-powered car

Snip a hole into the centre of what will be the top of your car.

Blow up the balloon and thread onto the end of a straw, holding tightly so the air doesn’t escape. Tape around the end to the straw.

Attaching the balloon to the car.

Thread the straw through the hole in the middle of your bottle and out of the bottle top. Place the bottle on the floor, and let it go!


Example #2

Making a card chassis balloon-powered car

Card chassis balloon powered car.

What you’ll need:

  • Bottle top lids (of equal size) x 4
  • Drinking straws x 4
  • Wooden barbeque skewers x 2
  • Sticky tape
  • Blu-tack
  • A4 Card
  • Scissors
  • Pliers (for an adult to cut the skewers)
  • Hand drill (for an adult to make holes in the bottle tops)
  • A standard-sized balloon
Materials.

Step One – Making the wheels & axels

SAFETY: This should be completed by a responsible adult or under supervision.

Place a piece of Blu-tack underneath the centre of the bottle top lid. Many bottle top lids already have a dimple to show the centre. If yours doesn’t, you will need to measure it to locate it.

Drill holes through the centres of the four lids.

Make wheel holes.

Next, very carefully push a wooden BBQ skewer through the hole, away from your hands.

You can now thread your skewer through a drinking straw.

Making the axels.

Next, add another bottle top lid onto the other end of the drinking straw to hold the straw in place. Snip the sharp end of the skewer off with a pair of pliers. Once you’ve done this, you can now repeat this step to create the other axel for your car.

Step Two – Making the chassis

Place another two drinking straws over the wheel axles to make a triangle shape. Tape these into place. It can help to keep the car still whilst you are doing this – You can temporarily hold the wheels in place by taping or blu-tacking them to your tabletop or work surface.

Next, using the length of the A4 card, draw and cut out two simple shapes to make the sides of your car (see the image below). Make sure these are mirror images of each other. If you wanted, you could also try out different shapes and sizes to see how it affects the performance of the car.

Tape one piece of card to the side of your car, attaching the tape to the straws. Bend the card round to create a corner, and tape this into place. Repeat this step to create the other side of the car. Fold the points of the card inwards and tape them into position. Cut a curved shape into the car body (for the balloon to rest on) and curve the sides.

Constructing the balloon powered car.

Finally, blow up a balloon (holding the end) and tape it to the sides and front to hold it in place.

Now place your balloon-powered car on the floor, and watch it go!

Key Questions:

• Does filling the balloon with more air affect speed / distance?
• What happens if you add two straws?
• What happens if you add two balloons?
• Does the size of the wheels affect speed / distance?
• How does the weight of the car affect speed / distance?
• How could you increase the grip of the wheels?

Other design considerations:

  • Try changing the size of the wheels
  • Use different length axels
  • Change the length of the straws
  • Does the shape of the car change its speed?
  • Add more balloons
  • You could even try adding a propeller

Extension Idea:

Wind-powered car

Try adding a paper or card sail, using drinking straws to support it. You could add a striking design to your sail. We folded the top of the sail over and snipped the centre to fold it together, then taped it into position.

Place a fan or hairdryer (with adult supervision) behind your cars and watch them go!

Wind powered cars.

Balloon and wind powered cars.

Interested in saving energy?
Check out these energy-saving tips and ideas to help protect the environment.

Looking for more fun STEM activities?
Have a go at building your own spectroscope to explore the electromagnetic spectrum.