Noun

Singular lever

Plural levers

lever (plural levers)

1. (mechanics) A rigid piece which is capable of turning about one point, or axis (the fulcrum), and in which are two or more other points where forces are applied; — used for transmitting and modifying force and motion.
   1. Specifically, a bar of metal, wood or other rigid substance, used to exert a pressure, or sustain a weight, at one point of its length, by receiving a force or power at a second, and turning at a third on a fixed point called a fulcrum. It is usually named as the first of the six mechanical powers, and is of three kinds, according as either the fulcrum F, the weight W, or the power P, respectively, is situated between the other two, as in the figures.
2. A small such piece to trigger or control a mechanical device (like a button)
3. (mechanics) A bar, as a capstan bar, applied to a rotatory piece to turn it.
4. (mechanics) An arm on a rock shaft, to give motion to the shaft or to obtain motion from it.

In physics, a lever (from French lever, "to raise", c.f. a levant) is a rigid object that is used with an appropriate fulcrum or pivot point to multiply the mechanical force (effort) that can be applied to another object (load). This leverage is also termed mechanical advantage, and is one example of the principle of moments. A lever is one of the six simple machines.

Early

The earliest remaining writings regarding levers date from the 3rd century BC and were provided by Archimedes. "Give me a place to stand, and I shall move the earth with a lever" is a remark of Archimedes who formally stated the correct mathematical principle of levers (quoted by Pappus of Alexandria).

It is assumed that in ancient Egypt, constructors used the lever to move and uplift obelisks weighting more than 100 tons .

Force and levers

The force applied (at end points of the lever) is proportional to the ratio of the length of the lever arm measured between the fulcrum (pivoting point) and application point of the force applied at each end of the lever.

Mathematically, this is expressed by M = Fd, where F is the force, d is the distance between the force and the fulcrum, and M is the turning force known as the moment or torque.