Watching the Wheels Go 'round and 'round

Age 7 to 11 Challenge Level:

You may find it helpful to find a toy with wheels or a wheel from a construction set, then to mark a point on the wheel and watch it turning. You could compare this with a differently sized wheel.
How many centimetres are there in a metre ... in two metres?
How many metres are there in a kilometre?
Which wheel will turn the most during the journey?