The lever is a rigid bar that is supported at one point. There are two arms in every lever. There is the effort arm and the load arm. The support on the lever is called the fulcrum. There are three classes of levers, Class 1, Class 2 and Class 3. Each are classified by location of the fulcrum, the input force and the output force. Some examples of levers are the Pulley, the wheel and axle, human levers and other common levers. Each levers have different features that impact their mechanical advantage. The mechanical advantage is the amount in which a machine can multiply the input force to find the output force.
