Horsepower and Speed for Dummies

Convert horsepower to MPG

Probably nothing an internet freelancer does gets our attention faster than answering the unanswerable question. Donald Rumsfeld and his "unknown unknowns" aside, some questions are either so vague or mindless as to be unanswerable, and some simply don't give enough information to allow a useful answer. Today we'll take a look a multiple DotD winner Chance E. Gartneer (an anagram of his real name, we presume) and his alleged instructions (originally on Synonym Science, since moved to Sciencing.com) for the nonsense topic "How to Convert Horsepower to Miles per Hour."¹

OK, let's break this down. One horsepower equals 550 foot-pounds per second, which kinda translates to "the amount of energy necessary to move 550 pounds one foot in one second." Got it? So next, let's consider miles per hour: that's a measure of distance per unit time. If we attempt to convert from "weight in distance per time" to "distance per time," we have to set up an equation sort of like this one:

weight / (distance / time) =  (distance / time)

As stupid as that looks, we could apply typical mathematical operations to our "equivalence equation" and cancel the (distance / time) terms, which would leave us with weight, which doesn't cancel out. In other words,

It is impossible to convert horsepower to miles per hour without knowing AT LEAST the mass involved. Idiot!

That didn't stop Gartneer, however. No, his instructions are Multiply the amount of horsepower by 33,000 to convert it into lb.ft./minute... Divide the amount of horsepower by the amount of power or thrust Multiply that number by 0.0113636364, which is the conversion constant from feet per minute to miles per hour... We especially liked the instructions to divide the amount of horsepower by the amount of power. We suspect the answer would be 1...

OK, so given a 35-horsepower engine (like that in a 1963 Volkswagen Beetle or a rather large lawn tractor), the answer using Gartneer's instructions is... wait for it... 13,509 MPH. Heck, according to Chance, you can achieve escape velocity and put the Beetle in orbit with just a 67-horsepower engine!

No, idiot, you can't. You can't make this conversion without AT LEAST some mention of the mass of the object to which that power is applied. It also helps to have terms for such things as friction and gravity, but those are a bit too "science-y" for the likes of Gartneer, who is hereby awarded his fourth Dumbass of the Day award. Happy New Year, "Chance"!

¹ Ha! Leaf Group hired someone else to rewrite this, and Chance's rubbish is gone forever... except that you can still find it with the Wayback Machine at archive.org (look for the URL   classroom.synonym.com/convert-horsepower-miles-per-hour-2802.html)

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