Mechanical advantage is force-amplifying effectiveness of a simple machine, such as a lever, an inclined plane, a wedge, a wheel and axle, a pulley system, or a jack-screw. The theoretical mechanical advantage of a system is the ratio of the force that performs the useful work to the force added, assuming there is no friction in the system. Practically, the actual mechanical advantage will be less than the theoretical value by an amount based on the amount of friction.
