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.