How does the distance between the effort and the fulcrum affect the mechanical advantage of the lever?

The mechanical advantage of using a lever is affected by
the distance between the effort and the fulcrum and by the placement of the load. You
need to consider both of those variables.

When the fulcrum
is centered between the load and the lift, the amount of effort exerted to push down on
the lever equals the amount of the load being lifted on the other end. This is called a
first class lever. If the distance between the effort and the fulcrum is increased, the
effort needed to raise the weight decreases
proportionately.

A second class lever places the fulcrum at
one end, the weight in the middle, and the lifting effort at the other end of the lever.
More effort is required to lift a given amount of weight with this arrangement, but the
effort doesn't have to be exerted over as great a distance as with a first class
lever.

A third class lever has the fulcrum on one end, the
weight on the other end, and the lifting effort in the middle of the lever. This
requires the most lifting effort.