When a wheel is affixed to an axle of a smaller diameter, a mechanical advantage can be gained. This is essentially another form of a lever.
![Wheel and Axle Illustration](https://engineeringtechnology.org/wp-content/uploads/2022/12/Wheel-and-Axle.png)
The mechanical advantage provided by this arrangement can be calculated as follows:
![](https://engineeringtechnology.org/wp-content/uploads/2022/12/Wheel-Mechanical-Advantage.png)
Notice that this arrangement is really just another way of making a lever.
![](https://engineeringtechnology.org/wp-content/uploads/2022/12/Wheel-as-a-Lever.png)
Wheels are also used to reduce friction via rolling contact.