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
(598kb)

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 forwards in the opposite direction (the reaction).

Example #1
Making a 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)

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

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 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.

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.

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.

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.

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

Example #2
Making a 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

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 to locate this.

Drill holes through the centres of the four lids.

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.

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 axels 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 a 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 card inwards and tape into position. Cut a curved shape into the car body (for the balloon to rest on) and curve the sides.

Finally, blow up a balloon (holding the end) and tape it into position on 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 the speed of the car?
Add more balloons
You could even try adding a propeller

Extension Ideas:
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 and taped it into position. Place a fan or hairdryer (with adult supervision) behind your cars and watch them go!