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How does a wheel and axle increase force?

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A diagram displays six types of simple machines with labeled illustrations: inclined plane, wedge, screw, lever, wheel and axle, and pulley, each shown with real-world examples like ramps, axes, screws, seesaws, door handles, and pulleys lifting objects. — simple machine Six simple machines for transforming energy into work.

The wheel and axle is a simple machine that amplifies force by utilizing the difference in radii between two connected components, such as drums or gears, rotating on the same shaft.12

When a force is applied to the larger radius (the wheel), it creates a turning effect on the shaft that is sufficient to overcome a larger force acting at a smaller radius (the axle). The mechanical advantage of this system is determined by the ratio of the radius of the larger component to the radius of the smaller component.12

In practical applications like lifting weights, ropes are wrapped around drums of different diameters. By pulling the rope on the larger drum, the operator can lift a heavier load attached to the smaller drum because the input force is multiplied by the ratio of the radii. While the theoretical mechanical advantage is defined by these dimensions, the actual force amplification is slightly lower due to the effects of friction.2