what is a first class lever

A first class lever is a type of lever where the fulcrum is located between the load and the effort. When an effort is applied to one end of the lever, a load is applied at the other end of the lever. In a first class lever, the effort (input force) moves over a large distance to move the load a smaller distance, and the fulcrum is between the effort and the load. As the ratio of effort arm length to load arm length increases, the mechanical advantage of a first class lever increases. Examples of first class levers include a teeter-totter, a car jack, and a crowbar.