When you look at caterpillar tractors (like the one on the left that Sir Edmund Hillary used when he travelled to the South Pole) you can see the big tracks that bite into the snow and ice.

On the drawing of a tank, you can clearly see similar tracks, but they are driven by a series of wheels.

What are the advantages of this kind of use of the wheel, and in what conditions would such tracks be most useful?

Many of you may have used a skateboard. The wheels on a skateboard are different to the wheels on a car in some ways, but similar in others.

Can you compare the two kinds of wheel in a T-chart?

Why are they more suitable for the conditions they are used in?

Trains use metal wheels that grip a metal track. This has many advantages, but it also has some disadvantages.

When you go to MOTAT, have a close look at the train wheels.