Why did the racer move?

When you released the balloon, air rushed backwards through the straw.

Pushing the air backwards created a force in the opposite direction, pushing the car forwards.

This is called Newton’s Third Law of Motion — forces come in pairs.

The balloon pushes the air backwards, and the air pushes the racer forwards.

Where did the racer get its energy?

Blowing up the balloon stretches the rubber and stores elastic potential energy.

When you let go, the balloon contracts and forces the air out. Some of that stored energy is transferred into the movement of the car.

A bigger balloon may store more energy — but does that always mean the racer will travel further?

That’s something you can test!

Why do the wheels and axles matter?

The wheels need to turn freely so the racer can keep moving.

Friction between the axles and other parts of the car can resist motion and slow it down. If an axle rubs, bends or isn't straight, some of the balloon's energy is wasted overcoming that friction.

But friction can also be useful. The wheels need enough traction with the floor to roll without slipping.

Can you make the racer travel further?

Absolutely!

Try changing one thing at a time — the amount of air in the balloon, the mass of the car, the wheel traction or even the direction of the straw.

Measure how far the racer travels and compare your results.

A small change could send Alex’s racer much further!

And there’s even more science hiding inside your runaway racer...