Force-amplifying effectiveness of a simple machine (lever, wedge, wheel and axle, pulley, or screw). The theoretical mechanical advantage of a system is the ratio of the force that performs the useful work to the force applied, assuming there is no friction in the system. In practice, the actual mechanical advantage will be less than the theoretical value by an amount determined by the amount of friction.

Learn more about mechanical advantage with a free trial on Britannica.com.