How does friction affect the mechanical advantage of a machine?

Friction reduces the actual mechanical advantage of a machine, causing it to perform below its theoretical potential. While the theoretical mechanical advantage is calculated assuming a frictionless system, in practice, friction ensures that the work output is always less than the work input.12

Because friction dissipates energy, the actual mechanical advantage—defined as the ratio of the output force (load) to the input force (effort)—is always lower than the theoretical value. While friction significantly impacts this force-modifying function, it generally does not affect the velocity ratio, which is determined by the machine's geometry and motion.12

To mitigate these losses, lubrication is often employed to reduce friction between sliding surfaces, thereby improving the machine's efficiency.3