The lever is probably the most commonly used simple machine. A lever is a rigid bar or solid
object that is used to transfer force.
With a pivot, the lever can be used to change the force that is applied (effort), alter the direction,
and change the distance of movement. An effort, a pivot, and a load are three features that are
common in every lever.
Depending on the positions of these shared features, you can distinguish between first, second,
or third class levers.