Balloon-powered car

Science concept

When air moves in one direction, it forces something to move in the opposite direction.

Special instructions

Drivers: start your engines! Fuelling up the car with pressurised air.

Teachers should conduct their own risk assessment of this activity.

Class time required: 30 minutes

Materials

• 4 plastic lids from soft-drink or water bottles. These lids will be the wheels of the car. Use a hand-drill to make a hole in each lid, just big enough for a bamboo skewer to fit through.
• Rectangle of thick corrugated cardboard (15 cm x 10 cm)
• Straight straw
• Bendable straw
• 2 bamboo skewers
• Balloon
• Rubber band
• Masking tape
• Scissors
• Plasticine
• Coloured pencils and decorations

What to do

1. Cut the straight straw in half. Tape one half-straw at one end of the cardboard, across the shorter side and tape the other half-straw at the other end.
2. Thread a skewer through each half-straw to make the car axles.
3. Thread the wheels (plastic lids) onto the skewers and use plasticine to hold the wheels in place.
4. Cut the long part of the bendable straw to the same length as the short part.
5. Blow up the balloon and let it down a couple of times to stretch the rubber.
6. Place the neck of the balloon over one end of the bendable straw and fasten it using the rubber band.
7. Turn the cardboard over and tape the bendable straw along the length of the car so the balloon rests on the cardboard. The straw should poke over the other end.
8. Inflate the balloon by blowing through the straw. Pinch the balloon so the air doesn’t come out.
9. Place the car on a clear, smooth surface and let the balloon go.

What’s happening?

Air rushes out of the balloon and through the straw in one direction and this forces the car to move in the opposite direction.