A lever is a rigid bar or rod that can pivot about a fixed position. This fixed position is called a fulcrum. Examples of levers include a seesaw, a crowbar, and a bottle opener. A lever is a type of simple machine.

Simple machines are the basic components of complex machines, such as a bicycle or an automobile. A machine is used to ease a load. Simple machines include the lever, wheel and axle, pulley, inclined plane, wedge, and screw. These machines can change the strength or direction of a force in order to do work. When a person does work on a machine, he or she is transferring energy to the machine. The machine then uses that energy to perform work on another object. The machine, therefore, transfers its energy to the object. Work is performed whenever a force moves an object. The amount of work done...