What Is lever.
There was this guy in Sicily , Archimedes:
http://www.math.nyu.edu/~crorres/Archimedes/Lever/LeverIntro.html
http://en.wikipedia.org/wiki/Lever
http://www.math.nyu.edu/~crorres/Archimedes/Lever/LeverIntro.html
http://en.wikipedia.org/wiki/Lever