Why Is Engine Power Measured In 'Horsepower'?

Why Is Engine Power Measured In 'Horsepower'? 

Why Is Engine Power Measured In 'Horsepower'?  Well, the reason is simply historical. Explanations.

At the end of the eighteenth century, horses were the most used means of moving loads and were also used to operate machinery, for example to raise water wells. With the invention of the steam engine, it was necessary to establish a conversion between the power of this engine and that which can be obtained from a horse. The goal was, for example, to answer this kind of question: what power must a steam engine have to replace a horse extracting water from a well?

James Watt and the horsepower

The great British scientist James Watt, like others before him, attacked this problem and he found a solution. He took as reference the power needed for a horse to run a grain mill and used the units of his country: pounds (lb), feet (feet, or ft) and seconds. Thus was born the "horsepower".

Value of a horsepower

The power unit is, later, become ... the watt (W). This is defined in the SI (International System) as a newton.meter per second.

A horsepower, or hp, is worth 745,699,872 watts.

Value of a horsepower

The rest of the world, using the metric system, defined "horsepower" as the power developed by a horse to go up 1 m to a mass of 75 kg in 1 s. A mass of 1 kg weighs 9.81 newtons, because the value of Newton is given by the acceleration of gravity (due to Earth's gravity) and is, by convention (it is an average), 9.81 m / s / s.

A horsepower of the metric system, or horse, is therefore 1 s x 75 kg x 9.81 m / s / s, or 735,498.75 W.

The "horsepower"  is the power developed by a horse to go up 1 m a mass of 75 kg in 1 s, or 735,498.75 W. (Attention: the horsepower of the metric system should not be confused with the horsepower, mentioned above, which is worth 745,699,872 W.) © Wikipedia, CC by-sa 3.0

Tax horses, horsepower ...

When steam engines began to replace horses, their power was expressed in horsepower or horsepower. The habit continues, and we keep the hp and the horsepower, to which were added the electric watt, the fiscal horses (CV, an administrative value) and even, for the cars, the horses SAE and the horses DIN .. While it would be enough for everyone to count in watts!