The factor by which a mechanism such as a pulley system multiplies the force or torque applied to it is called

• A. Efficiency
• B. Mechanical advantage
• C. Power Ratio
• D. Leverage Factor

Answer: (B)

Mechanical advantage is the factor by which a mechanism multiplies the input force or torque. In a pulley system, the rope segments share the load, so the system can exert a larger output force than the force you apply. The ideal mechanical advantage equals the number of rope segments supporting the load, so with two segments you can lift about twice the input force (ignoring friction), while you must pull a longer distance. Real systems aren’t perfect—friction and other losses reduce the actual advantage. This concept is different from efficiency, which compares useful output work to input work, and from other terms that aren’t standard for describing how force is multiplied.