Here’s Why Horsepower Is A Dumb Unit To Calculate An Engine’s Power


Horsepower is mostly the first term that people throw out while boasting about their cars’ power, but is it actually the best unit to measure a car’s power on the wheels? Jason Fenske at Engineering Explained thinks of it as wrong.

A quick fact, power is defined here as work overtime, which, for cars, the amount of force needed to drive a car a given distance, divided by the time it takes to complete that distance.

Horsepower was first suggested by James Watt. He was also the inventor of the practical steam engine. Knowing his engine would essentially compete against horses, Watt came up with a method to compare machines and animals’ power output.

The way Watt defined horsepower is contradicted, but it’s thought Watt based it on a horse turning a mill. The measurement is based on the horse walking a 12-foot diameter circle to turn a shaft and using 180 pounds of force on that shaft. But these figures are unreasonable.

Horses don’t all have the same strength, and it looks like Watt generally placed the amount of force in his writings, Fenske noted. Bottom line, one horsepower equals one horse lifting 550 pounds one foot in one second.

This unit of power was developed by James Watt in the 1700s. And who knew all these years later we’d still be using the unit that primarily was created to compare steam engines to horsepower.

The video below goes through Watt’s work to discuss it in simple terms. It also looks at metric horsepower too: PS, CV, and many other abbreviations.

No wonder metric or imperial, horsepower as a unit that is completely senseless. The video contains learning as to what unit we should actually be used at large.


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