A lever consists of a fulcrum, a force or effort, and a resistance. The fulcrum is the point at which the lever pivots, the effort is the point at which force is applied, and the resistance is where the work output is done. The distance from the fulcrum to the effort is called the effort arm, and the length from the fulcrum to the resistance is referred to as the resistance arm.
Levers come in three classes: A first class lever situates the fulcrum between the effort and the resistance, for example a seesaw. A second class lever situates the resistance between the fulcrum and the effort, such as a wheelbarrow. A third class lever situates the effort between the fulcrum and the resistance, such as a fishing pole.
Broader Topics Related to Levers
The most basic forms of machine: Levers, pulleys, wheels, inclined planes, screws, and wedges