What is a screw classified as in terms of simple machines?

A screw is classified as a device that converts rotational force into linear force. This classification stems from the fundamental function of a screw; when you turn it (apply a rotational force), the threaded design allows it to move linearly along its axis, either driving into a material or pulling two objects together.

This action highlights how screws facilitate the process of fastening items, demonstrating their utility in everyday applications. The spiral thread of a screw acts like an inclined plane, but instead of allowing for linear movement solely by gravity, it precisely converts the circular motion into axial motion. This conversion provides the ability to exert considerable force when the screw is driven into materials.

While the other choices touch on functions or roles of screws, they do not encapsulate the primary mechanical principle that defines a screw's operation. For example, while a screw indeed can amplify mechanical advantage and serves as a fastening device, the core function emphasizing its classification as a simple machine is its ability to translate rotational force into linear motion.