DIY: Balloon-Powered Car | Tinkerer Box Blog

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Balloon-Powered Car

Stem Activities

Ages: 6-8

Less than 30 minutes

Grownup needed

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Create a car powered by a balloon using recycled materials. You can make several and race them against each other to test which factors affect your car's speed and travel distance.

Materials Needed

Cardboard
4 bottle caps
pencil
wooden sticks
tape
balloon
plasticine
paint palette
paint
paintbrush
3-4 straws
ruler
scissors

An assortment of craft supplies lies neatly arranged on a light woodgrain surface, viewed from directly above. The items include a piece of brown cardboard, four white plastic bottle caps, a roll of gold glitter tape, a blue pencil, two thin wooden dowels, a deflated lime green balloon, a small lump of teal modeling clay, two small tubes of paint (yellow and teal), a pair of blue scissors, a blue paintbrush, a yellow straw or stick, and a clear plastic ruler. This flat lay suggests materials gathered for a children's craft project.

Step-by-step tutorial

Step 1

Cut the cardboard into a 15cm x 10cm rectangle.

A rectangular piece of light brown cardboard sits on a light-colored wooden surface. Black lines and text indicate its dimensions: 15cm wide and 10cm tall. The image is a simple, straight-on view of the cardboard piece, emphasizing its size and plain surface.

Step 2

Using paint and paintbrush, paint the rectangular cardboard in your favourite colours. Wait patiently for the paint to dry.

Two hands are shown in the process of painting a piece of cardboard light green. One hand holds the cardboard, which is mostly covered in the light green paint, against a light woodgrain background. The other hand holds a paintbrush with orange bristles and a blue handle, applying more paint to the corner of the cardboard.

Step 3

Using scissors, cut two 10cm lengths from the straws.

Two hands are shown cutting a yellow flexible drinking straw with a pair of scissors. One hand holds the straw against a light woodgrain background, while the other hand operates the gray-handled scissors, cutting the straw. The focus is on the action of cutting the straw.

Step 4

Cut two 15cm lengths from the wooden sticks.

Two hands are shown cutting a thin wooden dowel with scissors. One hand holds the dowel against a light woodgrain background, while the other hand uses black-handled scissors to cut the dowel. The image focuses on the action of cutting the dowel.

Step 5

Turn over the dried cardboard and draw 2 parallel guide lines as shown.

A rectangular piece of light brown cardboard rests on a light woodgrain surface. Two vertical black lines divide the cardboard into three equal sections. Black lines and text indicate that the outer sections are each 3cm wide. This image illustrates measurements marked on the cardboard, likely for cutting. A faint trace of light green paint is visible along the bottom edge of the cardboard.

Step 6

Take the 2 10cm straws and secure them on the drawn guide lines using tape.

Two hands are shown attaching yellow straws to a piece of cardboard. The cardboard, placed on a light woodgrain background, has two short yellow straws horizontally positioned, one near the top and the other near the bottom. Bright yellow tape secures the straws to the cardboard. One hand holds the cardboard steady, while the other hand adjusts the tape around one of the straws. A trace of light green paint is visible along the bottom edge of the cardboard.

Step 7

Place each wooden stick through the secured straws.

Two hands hold a piece of light brown cardboard against a light woodgrain background. Two thin wooden dowels are attached horizontally to the cardboard, one near the top and the other near the bottom. Sections of yellow straws are taped to the center of each dowel with bright yellow tape. The hands hold the dowels, extending beyond the edges of the cardboard. A faint trace of light green paint is visible along the bottom edge of the cardboard.

Step 8

Next, place plasticine under the bottle caps and use a sharpened pencil to make a hole in the centre of each cap. Make all 4 wheel caps this way.

Two hands manipulate a pencil and a small plastic bottle cap on a light woodgrain surface. One hand holds the teal-colored base of the bottle cap, which has a white interior and lid. The other hand holds a blue pencil with a red eraser, positioning the pencil's point in the center of the bottle cap's white lid. The image suggests the pencil is being used to mark or pierce the center of the cap.

Step 9

Then insert the bottle caps onto the wooden sticks.

Two hands display a simple toy car constructed from a piece of light green painted cardboard and four white plastic bottle caps as wheels. The car rests on a light woodgrain surface. Short wooden dowels, acting as axles, connect the bottle cap wheels to the cardboard body. The hands hold the car from the sides, gently touching two of the wheels.

Step 10

Take a straw and bend it.

Two hands hold a flexible yellow drinking straw bent into a shallow V shape against a light woodgrain background. The bendable portion of the straw is located near the bottom of the V. The hands gently grip the straw on either side of the bend.

Step 11

Insert the shorter end of the straw into the balloon and secure it with tape, sealing the balloon's opening. Ensure the balloon is completely sealed.

Two hands are shown attaching a deflated lime green balloon to a yellow straw against a light woodgrain background. The neck of the balloon is stretched over the end of the straw. A piece of yellow tape is being wrapped around the connection point to secure the balloon to the straw. One hand holds the balloon and straw while the other hand adjusts the tape.

Step 12

Finally, use tape to secure the longer end of the straw to the cardboard, ensuring the straw's end extends 3.5cm beyond the car body.

Two hands hold a small, light green cardboard car on a light woodgrain surface. The car has four white bottle cap wheels attached with wooden dowels as axles. A yellow straw is taped to the top of the car, and a deflated lime green balloon is attached to the other end of the straw. The straw extends off the back of the car. A measurement line indicates the straw extends 3.5cm beyond the back edge of the cardboard.

Step 13

Now, blow up the balloon through the straw and pinch the straw to prevent air from escaping. Place your balloon car on a table or floor. Let go! See how far your balloon car can travel.

A small, homemade balloon-powered car moves across a light wooden surface. The car is constructed from a piece of light green cardboard, with white bottle caps serving as wheels. A lime green inflated balloon is attached to the cardboard. As the air is released from the balloon, it propels the car forward, demonstrating a simple physics principle. The camera follows the car from a top-down perspective as it travels across the wooden surface.

The Science Behind It:

When you inflate the balloon, it stores potential energy (both in the stretched rubber and the compressed air inside). When you release the balloon, this stored potential energy converts into kinetic energy - the energy of motion. We can also explain this through mechanics: when the balloon deflates, the escaping air is pushed out from the back of the balloon; in turn, the air pushes the car forward. This is Newton's Third Law of Motion in action - for every action force, there is an equal and opposite reaction force.

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