A lever is a simple machine that can be used to lift a heavy load. They consist of a hinge or fulcrum and a rigid beam. Levers can be put into 3 classes depending on the location of the load, effort and fulcrum.
A lever consists of a rigid beam that moves across a hinge or fulcrum. The lever was identified as a simple machine by Archimedes, along with the pulley and screw. Archimedes is often quoted as saying “Give me a place to stand and I will move the Earth.” Levers can exert a large force over a small distance on one end by exerting a small force over a large distance at the other. An ideal lever does not lose or store energy, so the power in is equal to the power out. This relationship can be used to calculate the mechanical advantage as the ratio of the distances from the fulcrum for the effort and the load.
It is impossible to say who invented the lever. Levers have been used throughout history to lift heavy objects that humans would otherwise not be able to lift. They were used by the ancient Egyptians to move heavy blocks during the construction of the pyramids. Levers are still used in construction today, like when builders remove nails using the claw on a claw hammer, but are also used in many facets of everyday life.
| Class | Description | Examples |
|---|---|---|
| Class 1 | Levers that have the load and the effort on opposite sides of the fulcrum |
|
| Class 2 | Levers that have the load in the middle of the beam, with effort on one side and the fulcrum on the other |
|
| Class 3 | Levers that have the effort in the middle with the load and fulcrum at either end |
|