When you hear the term “horsepower,” what do you think of? Perhaps a large engine powering a fast car, a boat traversing the ocean, or a plane zooming through the sky. Or maybe, like a true equestrian, you envision a horse-drawn carriage or a draft horse pulling a plow. In all these instances, horsepower is at the core, so how did this phrase come to be?
What is Horsepower?
Horsepower is the term used to express how much power an object can create. Practically, it is the rate at which work is done. One horsepower is equal to moving 550 pounds the distance of one foot in one second.
The history of the phrase “horsepower” originated in the 18th century, by James Watt, a Scottish engineer and inventor of the first practical steam engine. Watt used “horsepower” as a marketing tool when he compared the amount of work his steam engine could produce in relation to a horse. The steam engine was a new invention and people were skeptical that a man-made machine had enough power to accomplish the work that their horse could.
How is Horsepower Measured?
Watt set out to scientifically compare the two. By determining that a horse could turn a mill wheel with a 24-foot diameter 144 times in an hour, he calculated that a horse could produce 33,000 foot pounds per minute. That is a lot of work! At that time, Watt’s steam engine could produce five horsepower, or the amount of work five draft horses could do in a day.
Is a Horse Really One Horsepower?
In Watt’s determination of horsepower, he based his calculations off the average rate of work a draft horse could do over one full day. However, one horse does not always produce one horsepower. In fact, over a short period of time a horse can exert up to 14.9 horsepower! The power one horse can produce is affected by that horse’s physical fitness and breed.
Breeds like Thoroughbreds and Quarter horses can often produce more horsepower because they are bred and trained to work. Large draft horses that have lots of muscle can also produce a significant amount of power. Smaller horses, like Arabians and ponies, produce less power.
In comparison, a healthy human adult can produce 1.2 horsepower for a short amount of time and a highly trained athlete can produce about 2.5 horsepower. A typical car can produce 150-200 horsepower.
Though the term horsepower isn’t a literal description, it is still used to describe engine output to this day. So next time you see how much horsepower a vehicle has, remember the origin of the term, and imagine a big ol’ draft horse turning a mill wheel 144 times in an hour.
Featured Image: iStock.com/TeresaKasprzycka
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