12 ms·

> When it comes to domains where consistency does matter, we just don't do unit conversions. For instance, flight altitude is measured in feet, even when it's t

by nayuki 3y ago

> When it comes to domains where consistency does matter, we just don't do unit conversions. For instance, flight altitude is measured in feet, even when it's thousands of feet, instead of miles. If you're flying an airplane at 30,000 feet, who cares how many miles that is? Wrong. https://en.wikipedia.org/wiki/Gliding_flight#Glide_ratio https://en.wikipedia.org/wiki/Gliding_flight#Glide_ratio Your plane is up at 30000 feet and your engines are out. The nearest airport is 47 nautical miles out. The plane has a glide ratio of 15. Will you make it? It's easy in metric: 9.1 km altitude, 87 km distance. > Again, even "metric" countries don't commit to the bit here; name me a country where the highway speed limit is in meters per second. I actually much prefer metres per second. It makes things like kinetic energy calculations easier. If I wanted to know the KE of a 1500 kg, 100 km/h car, I would first need to convert to m/s. Ditto the kilowatt-hour; it needs to die in favor of megajoules.

philwelch 3y ago
> Your plane is up at 30000 feet and your engines are out. The nearest airport is 47 nautical miles out. The plane has a glide ratio of 15. Will you make it? Nautical miles and statute miles are different units anyway, so my initial assertion--that you would never convert flight altitude to statute miles--is still correct. Glide ratio varies according to speed; the plane might have a glide ratio of 15 at one speed but a different glide ratio at a different speed. So in practice, the real world version of this word problem is more complex than you make it out to be, and pilots' handbooks will commonly have tables of glide distances to consult for this reason. > If I wanted to know the KE of a 1500 kg, 100 km/h car, I would first need to convert to m/s. You've adequately demonstrated that metric is more convenient for arbitrary word problems that you've provided. Real world applications is what I'm less convinced about.

by nayuki 3y ago

philwelch 3y ago

> Your plane is up at 30000 feet and your engines are out. The nearest airport is 47 nautical miles out. The plane has a glide ratio of 15. Will you make it? Nautical miles and statute miles are different units anyway, so my initial assertion--that you would never convert flight altitude to statute miles--is still correct. Glide ratio varies according to speed; the plane might have a glide ratio of 15 at one speed but a different glide ratio at a different speed. So in practice, the real world version of this word problem is more complex than you make it out to be, and pilots' handbooks will commonly have tables of glide distances to consult for this reason. > If I wanted to know the KE of a 1500 kg, 100 km/h car, I would first need to convert to m/s. You've adequately demonstrated that metric is more convenient for arbitrary word problems that you've provided. Real world applications is what I'm less convinced about.