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Balloon Powered Car

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Do people say you’re full of hot air? Why not use it to power your brand new balloon powered car?! Just make sure you use a red balloon…it’ll go faster.

What you need

  • 4 plastic lids from soft-drink or water bottles.
  • hand drill or power drill
  • 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

Please note: an adult should operate the hand drill or power drill.

  1. The plastic lids will be the wheels of the car. Use a hand drill or power drill to make a hole in each lid, just big enough for a bamboo skewer to fit through.
  2. 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.
  3. Thread a skewer through each half-straw to make the car axles.
  4. Thread the wheels (plastic lids) onto the skewers and use plasticine to hold the wheels in place.
  5. Cut the long part of the bendable straw to the same length as the short part.
  6. Blow up the balloon and let it down a couple of times to stretch the rubber.
  7. Place the neck of the balloon over one end of the bendable straw and fasten it using the rubber band.
  8. 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.
  9. Inflate the balloon by blowing through the straw. Pinch the balloon so the air doesn’t come out.
  10. Place the car on a clear, smooth surface and let the balloon go.

What's happening?

After you put the car on a surface and let go of the straw, the air moves out of the straw in one direction and the car moves in the opposite direction.

Sir Isaac Newton developed three laws of motion in 1665 when he was only 23 years old. These laws revolutionised how science explained movement by describing how the forces acting on an object are responsible for the object’s motion.

Your balloon powered car is a good example of Newton’s third law of motion. It states, “To every action there is an equal and opposite reaction.” This means that if object A pushes on object B, object B pushes back on object A with the same amount of force. In the case of the balloon-powered car, the air is pushed out of the straw in one direction and the car is pushed in the opposite direction.

Newton’s third law of motion is perhaps the most widely recognised and incorrectly used of the three laws. Despite occurring all around us, Newton’s third law can be difficult to comprehend. For example, if you lean against a wall it is easy to imagine that your shoulder is pushing, or exerting a force, on it. It is less easy to realise that not only is the wall pushing on your shoulder, but that it is pushing with an equal amount of force.

Investigate!

Can you make your car go faster or further using the same amount of air? (Hint: Try changing the size of the wheels.)

Did you know?

Newton’s third law of motion can be observed in sports. For example, in swimming the swimmer’s stroke pushes on the water and the water pushes back on the swimmer propelling him/her forward. In kicking a football, the foot pushes on the ball and the ball pushes on the foot in the opposite direction with the same amount of force.