Today’s Wonder of the Day was inspired by Billy from Austin. Billy Wonders, “Why is it called horsepower?” Thanks for WONDERing with us, Billy!

When you think of strong animals, what comes to mind? You probably won’t think of a chicken. Or a pig. But you might imagine an elephant. There’s one animal, though, whose very name conjures up the image of power. What are we talking about? The horse…of course!

Big and brawny, yet graceful and fast, horses are an image of pure power. Their big muscles have helped them run fast and work hard for thousands of years. When early farmers plowed their fields with the first plows, they didn’t hitch them to the cows or the pigs or the chickens. Nope. They went straight for the most powerful animal on the farm: the horse.

And why shouldn’t they be strong? Just look at them! Horses are long, tall animals. Their frames are covered with huge muscles, ready to work.

Farmers recognized the value of horses thousands of years ago. Used for daily farm work, horses eventually were used for sport, too. Farmers would challenge each other to see whose horses could pull the most weight. This led to the modern sport of horse pulling, which you might see at a county or state fair in the summer.

So, just how strong are horses? It’s impossible to pin down a horse’s strength exactly, but some large horse breeds have been known to pull up to three times their own weight. That means they might pull up to 2,500 pounds or more!

Engineer James Watt was inspired by the strength of the horse when he came up with the term “horsepower” as a new unit of measurement. While working with horses lifting coal at a mine, Watt wanted a way to describe the power of the animals. Specifically, he wanted to measure how much energy it took a horse to raise coal out of the mine.

Using the term “horsepower,” Watt guessed that a horse could do 33,000 foot-pounds of work in one minute. That’s like saying a horse could lift 33,000 pounds exactly one foot in one minute. There are several other equivalent ways of expressing one horsepower:

  • lifting 1 pound 33,000 feet in one minute

  • lifting 1,000 pounds 33 feet in one minute

  • lifting 1,000 pounds 330 feet in ten minutes

  • lifting 100 pounds 33 feet in 6 seconds

It was an arbitrary estimate that wasn’t based upon any precise calculations. Yet it stands as a popular measurement still today! You’ll see horsepower referenced on all sorts of different engines, from cars and lawnmowers to chain saws and vacuum cleaners.

Most modern cars have between 100 and 200 horsepower. High-performance muscle cars might have upwards of 400-500 horsepower, though!

Watt’s name is associated with another unit of measurement of power: the watt. You’ve probably seen this measurement on light bulbs. Watt is a measure of energy used for electricity, but horsepower can be converted into watts. One horsepower is equal to 746 watts.

Standards: CCRA.L.3, CCRA.L.6, CCRA.R.1, CCRA.R.2, CCRA.R.4, CCRA.R.10, CCRA.SL.1

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