Which of the following is an example of a wedge?

A doorstop serves as an example of a wedge because it is designed to create a slope or incline, allowing it to force its way between two surfaces, such as a door and the floor. The fundamental principle behind a wedge is that it converts force applied to it into a force perpendicular to the surfaces it interacts with, effectively separating them. In the case of a doorstop, when pressure is applied (for example, by the weight of the door), the wider end of the doorstop pushes against the door, keeping it in a propped open position, while the tapered side fits snugly against the ground, preventing movement.

Other options do not represent a wedge as clearly. A screw is better categorized as an inclined plane wrapped around a cylinder, while a ramp also exemplifies an inclined plane, designed to assist in moving objects from a lower height to a higher height without the wedge-like action. A pulley, on the other hand, is a simple machine that changes the direction of a force and does not fit the definition of a wedge. Thus, the doorstop stands out as a clear representation of a wedge in this context.