More wheels and axle

How many wheels are there on a bicycle? Two . wrong! There are there.Apart from the two big wheels, there is the small toothed wheel to which the pedals are attached. It is called the chain wheel because it moves the chain when you pedal. The chain wheel and pedal system is another example of that simple machine, the wheel and axle. When you pedal your bike, the pedals (acting as the wheel) turn in a large circle, while the chain wheel (acting as the axle) turns in a small circle.  This means that the you apply to the pedals turned into a bigger force at the chain wheel.