What simple machine is described as a rigid bar that pivots about a fulcrum to multiply an applied force?

The description of a simple machine that is a rigid bar pivoting around a fulcrum accurately defines a lever. A lever functions by allowing an applied force to be multiplied, based on the distance from the fulcrum where the force is applied compared to the distance from the fulcrum to the point where the load is located. This mechanical advantage enables a small force applied over a longer distance to lift a larger load over a shorter distance.

In contrast, a pulley consists of a wheel on an axle designed to change the direction of a force, whereas an inclined plane is a flat surface set at an angle, which facilitates lifting by spreading the force over a longer distance. The wheel and axle work together as a combined mechanism to transmit force and motion but do not specifically align with the definition of pivoting about a fulcrum as described for a lever. Thus, the lever is distinctly characterized by its ability to amplify force through its structure and arrangement relative to its fulcrum.