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How does friction affect the efficiency of a simple machine?

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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.

Friction significantly impacts the performance of a simple machine by reducing its efficiency. In any mechanical system, efficiency is defined as the ratio of work output to work input. Because friction consumes a portion of the input energy, the work output is always less than the work input, resulting in an efficiency of less than 100 percent.1

Friction also affects the mechanical advantage of a machine. While the theoretical mechanical advantage assumes a frictionless environment, the actual mechanical advantage is always lower due to frictional losses. While friction reduces the force-amplifying effectiveness of a machine, it generally does not affect the velocity ratio, which is determined by the machine's geometry and motion-modifying function.21

In essence, friction acts as a resistive force that necessitates a higher input effort to achieve the same load, thereby limiting the practical utility of simple machines like the lever, pulley, or inclined plane.12