Why does a balloon car move forward?
Help your child connect backward-moving air with the forward push on the car.
Balloon car: discover thrust from escaping air
In a balloon car, air streams backward through the opening. The car is pushed in the opposite direction. The balloon holds only a limited amount of air: a wider opening can give a stronger push but also empty sooner.
Watch two things rather than distance alone: how strongly the car starts and how long air flows out. In the interactive lab, change the opening while keeping the air amount fixed. Compare the start first, then the whole journey.
„Which way will the air move, and which way will the car move?“
Try it together in the lab
- Begin with a prediction. You do not have to agree.
- Change Air opening from 8 mm to 12 mm; keep the amount of air unchanged.
- Compare how strongly the car starts and how quickly the balloon empties.
Next comparison: Compare smoother axles while keeping the air amount and opening unchanged.
Start the labAn activity away from the screen
With an adult, attach a balloon to a lightweight toy car so the opening points backward. Release it on a clear, level tabletop or floor. Balloons and small parts should be handled with adult supervision.