# Levers and how they work

By Barbara10Broek, 14th Jun 2011 | Follow this author | RSS Feed
Posted in Wikinut>Guides>Science>Physical Forces

Discusses how levels work and the classes of them.

## Simple Machine

A lever is a simple machine. It consists of a ridged bar which can turn around a fixed point called a fulcrum. A crowbar is a kind of lever and is used as a force magnifier to lift heavy weights by using smaller forces. The load at one end of the bar is overcome by a smaller force the effort applied at the other end. Such a lever is said to have a positive “mechanical advantage”. To achieve this the lever must obey the rule that applies to all force magnifiers the effort must move a greater distance that the load. To raise a heavy rock the effort applied at the end of the bar must move farther than the rock rises.

## Archimedes moving the world

After a study of levers Archimedes boasted that given a long enough lever and a place to stand and he could move the world. Of course to operate his lever he would have needed a fulcrum. In this old drawing Archimedes is using a crowbar, a typical class one lever which has the fulcrum between the load and the effort. For greatest mechanical advantage the load (the earth) must be close to the fulcrum and the lever must be long. During his study of levers discovered the law of the lever for balance the effort multiplied by its distance from the fulcrum must equal the load multiplied by its distance from the fulcrum.

## Classes of levers

There are three classes of </a><img src="http://www.assoc-amazon.com/e/ir?t=hubp0e225-20&l=as2&o=1&a=B001J4RTIC&camp=217153&creative=399701" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;]levers representing variations in the relative locations of the fulcrum, the load and the force. For a class 1 lever: The fulcrum is located between the applied force and the load, for example, a crowbar or a pair of scissors or a seesaw. For a class 2 lever the load is situated between the fulcrum and the force, for example, a wheelbarrow or a nutcracker. For a class 3 lever the force is applied between the fulcrum and the load, for example, a pair of tweezers or the human jaw bone.

Barbara10Broek