# Lifting machinery: levers Archimedes was one of the most important scholars regarding the levers and the conditions of equilibrium of bodies.

If two different weights P1 and P2 are suspended at the ends of a lever AB, to have a situation of equilibrium it is necessary to identify a point F on which to rest the lever; the point, called “fulcrum”, must be chosen so that the products of the weights for the respective measures of their distances from the fulcrum are equal.

## The levers

A lever is a simple machine consisting of a rod called a fulcrum that rotates around a point. Two forces act on the levers, Resistant Force, and the Driving Force. We have an equilibrium condition: br x Fr = bm x Fm A leverage can be:

• Advantageous, driving force is less than the resisting force;
• Disadvantageous, driving force is greater than the resisting force;
• Indifferent, driving force equal to resisting force.

The levers are also divided into those of:

First genus where we find the fulcrum between the point of application of the resisting force and the point of application of the driving force. these levers are in turn divided into Advantageous, Indifferent and Disadvantageous.

The second genus can be defined as such when the resisting force is between the fulcrum and the driving force. In these levers the arm of the driving force is always longer than that of the resisting force, which is why they are always advantageous.

Third kind are always disadvantageous because the arm of the resisting force is always greater than that of the driving force. An example can be the tweezers that in fact we only use to grab non-heavy objects, or our forearm.