explain what a lever system is and what it does?

Answer 1

It is actually a very complex system.
A lever system allows you to exercise
the physical properties of two
interconnected torque arms.

see: http://en.wikipedia.org/wiki/Torque

This is govern by the equation:

Torque=Force*Radius

Now given a system of two forces
connected by a beam at two radii
from a fulcrum (the reaction force required
because all actions have opposite reactions,
but we'll ignor that force)

F1*R1 = Tq1
F2*R2 = Tq2

If these torques are not equal,
you get motion (acceleration) in the system
around the fulcrum based on that torque
(that is...the net torque Tq1-Tq2)
and the moment of inertia (masses)
of the system. The system will accelerate
based on the equation:
(angular acceleration) = (Tq1-Tq2)/Inertia

Answer 2

When you have heavy objects to lift or move, a lever system provides us with a mechanical advantage that allows us to lift and move much heavier loads than would be possible without using lever systems.
A 100pound load could be lifted by applying only 25 pounds to the end of a lever, if the distance from the fulcrum, or lever support point to the load was 1 foot and the distance from the fulcrum to the applied lift force was 4 feet.