Which simple machine consists of a wheel on a fixed axle with a groove to support a sliding rope?

• A. Lever
• B. Screw
• C. Pulley
• D. Inclined plane

Answer: (C)

A pulley is a simple machine that uses a wheel on a fixed axle with a groove to guide a rope or cable. The groove keeps the rope in place as it runs around the wheel, and because the wheel is fixed, the main function is to change the direction of the applied force. This lets you lift a load by pulling in a convenient direction, such as downward, rather than lifting straight up.

The other options describe different mechanisms: a lever uses a rigid bar and a pivot to trade force for distance; a screw is an inclined plane wrapped around a cylinder, converting rotational motion into linear motion with threads; an inclined plane is simply a flat ramp that reduces the force needed over a longer distance.