Which best describes the function of a pulley?

A pulley is fundamentally designed to facilitate the lifting or lowering of objects with greater ease, which directly aligns with the definition of a simple machine. It operates by utilizing a wheel on an axle or shaft that allows a rope or cable to move smoothly. This setup significantly changes the direction of the force applied, making it possible for a person to lift heavy objects by applying less force over a greater distance. The efficiency gained through this mechanical advantage reduces the effort needed to overcome gravity, making tasks involving vertical movement much more manageable.

The other options diverge from the specific mechanical function of a pulley. For instance, measuring speed or generating heat do not involve the characteristics or operations related to pulleys. Additionally, a transportation vehicle represents a completely different concept unrelated to the function of lifting or mechanical assistance that a pulley provides.