In physics, mechanical efficiency is the effectiveness of a machine and is defined as
- <math>\mbox{Efficiency} = \frac{\mathrm{Mechanical Advantage}}{\mathrm{Velocity Ratio}}</math>
To show the effectiveness of a machine one must compare its work input to its work output. Efficiency is often indicated by a percentage, the efficiency of an ideal machine is 100%. Due to the fact that energy cannot emerge from nothing and the Second law of thermodynamics which states that the quality of energy will always decrease (transforming from mechanical energy to thermal energy) the mechanical efficiency of any machine will always be less than 100%.
