A first-class lever, in which the fulcrum is between the load and the effort, can aid in work by changing the direction of the force and by increasing the efficiency or mechanical advantage of the force applied. The force exerted on a first-class lever has greater mechanical advantage proportional to its distance from the fulcrum.
According to Ohio University, a lever is a simple machine which can make work easier. All levers consist of some kind of rod attached to a fulcrum, or a fixed location where the lever can pivot. A children's seesaw is one example of a first-class lever, because the fulcrum is in the middle of the moving lever and the forces are applied to either end. When one child pushes down on his end, the other end is provided with an upward force.
The law of equilibrium states that in a balanced lever, the product of the mass and distance at one end will equal the product of the mass and distance at the other end. If the masses are the same, both masses must be the same distance from the fulcrum for the lever to balance. However, if a 10 pound object is placed 2 feet away from the fulcrum on one side of the first-class lever, a 5 pound object must be placed 4 feet away from the fulcrum on the other side for the lever to be balanced.
According to CityOfTechnology.org, some examples of first-class levers in household tools are scissors and pliers.