What term refers to two wheels of different sizes that rotate together?

• A. Inclined Plane
• B. Lever
• C. Pulley
• D. Wheel and Axle

Answer: (D)

The concept is a wheel and axle, a simple machine built from a wheel attached to a smaller axle on the same axis. They rotate together, so they share the same angular speed, but the difference in their sizes lets you trade force for distance. If you push the larger wheel, you can generate a greater force at the axle depending on the radius ratio (the wheel radius divided by the axle radius), while the movement at the wheel covers more distance than the movement at the axle. This setup illustrates how rotating parts connected on one axis can amplify force or distance based on their sizes. The other options describe different mechanisms: an inclined plane changes height with distance, a lever uses a pivot to trade force for distance, and a pulley system changes the direction or amount of force with a belt or rope, not a pair of wheels rigidly linked to rotate together.