About horsepower

Ever wondered what it actually means when an engine has x horsepower? I did, so I looked it up, and here’s what I came up with.

Horsepower is a mechanical power unit and is really just watts by another name. One hp is ~750 watts. So if you have a vacuum cleaner with a 1500w rated engine, that’s two horsies for you. It’s really not that much.

The original definition of one hp is 33,000 ft-lb/min in funky imperial units, or 75kg*m/s in real units. And what this means is that an engine with 1hp can lift 75kg one metre high in one second flat.

Surprisingly enough, a trained human can easily do this, as the human peak power output is above 1hp.

How much horsepower does a horse actually have? Believe it or not, the sustained power output of a horse working for multiple hours is about 1hp. However, the peak power output of a horse can be almost 15 horsepowers.

So just how much power does a car engine have? Let’s say you have an average car of 1500kg with an average engine of 100hp. That’s 20 times the weight of 75kg, but 100 times the power of 75kg*m/s, so the engine could lift itself with the car 5 metres high in one second.

Since the sustained power output of a human is around 0.25hp, it would take a single person about 7 minutes to lift that car 5 metres high.

tl;dr: Your car is about 400 times stronger than you.

(On a sidenote: Horses aren’t that good at walking long distances and are beaten by humans on hot days.)

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