In physics, mechanical efficiency is the effectiveness of a machine and is defined as Physics (from the Greek, (phúsis), nature and (phusiké), knowledge of nature) is the science concerned with the discovery and understanding of the fundamental laws which govern matter, energy, space and time. ...

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%. The percent sign A percentage is a way of expressing numbers as fractions of 100 and is often denoted using the percent sign, %. For example, 45. ... An ideal machine is a machine that cannot exist in reality for a number of reasons: It is frictionless. ... The second law of thermodynamics is a theorem in physics regarding the directional flow of heat in relation to work and which accounts for the phenomenon of irreversibility in thermodynamic systems. ...

See also

• Thermal efficiency
• Electrical efficiency
• Internal combustion engine
• Electric motor