Which formula calculates the efficiency of a machine?

The formula that accurately calculates the efficiency of a machine is the one that measures the relationship between the actual mechanical advantage (AMA) and the ideal mechanical advantage (IMA). Efficiency is expressed as a percentage, reflecting how effectively a machine converts input work (or energy) to output work (or energy).

By using the formula involving AMA and IMA, efficiency gives a clear indication of how close a machine's performance is to its theoretical maximum. The ideal mechanical advantage represents the expected performance of the machine in a perfect scenario, whereas the actual mechanical advantage accounts for real-world losses due to factors like friction and deformation. Thus, dividing AMA by IMA and multiplying by 100% yields the efficiency percentage, providing insight into the machine's performance.

This understanding highlights the importance of considering both actual and ideal mechanical advantages to grasp a machine's efficiency comprehensively. The other formulas do not accurately represent efficiency as they either misinterpret the relationship between input and output work or confuse force relationships without addressing the overall work conversion process.