Pounds are properly force, but just as kilograms can be used as a unit of force (it annoys me, but apparently it's considered correct to use kg to mean 9.8 N), pounds get sloppily used for mass as well.
Correctly, the slug, not the pound, is the unit of mass in the fps system. It's the amount of mass which one pound of force will accelerate at one foot per second per second.
Uff. Acceleration conventionally is [unit of length] / [unit of time squared]. There's one problem. The other is that I can't readily see where the 32 comes from.
(I could say something about a system of units where there are multiples of 12, 16, 8, 4, 3, and things that are not multiples but something elses, but those are units of currency, not units of physics, and I shall leave the whole imperial measurement system alone just remarking that the imperial and colonial pound and pint are not the same just to confuse us modern metric morons.)
g = 32 feet per second per second. So it's a natural number to reach for when trying to remember relationships between units of mass and units of weight, if one's used the system long enough to remember g in it.
As for the rest of your comment, there are several reasons I strongly prefer the metric system if I'm going to need to do any calculations.
It's not just the dozens and sixteens; it's also the downright wonky constants you wind up with as a result. In mks some textbooks even round g off to 10 for end-of-chapter problems, and the only pain-in-the-butt conversion constant I remember having to deal with was when converting Joules to calories. (Unless I'm forgetting something involving coulombs.) Despite having been raised in fps and living in a culture that continues to use it most of the time, I really don't want to do any math or science in fps. Meters, kilograms, Newtons, Kelvins, and liters for me, thank you very much.
(Though there is something to be said for the number of convenient factors that go into Babylonian base-60 measurement systems, as well...)
(Doh! Okay, I do remember one other oddball constant: liters/mole @ STP. But ISTR that being easy to remember because it was the same digits as the altitude of geosynchronous orbit with a different exponent, right? And then there's G and Avogadro's number, but those aren't everyday outside-the-lab numbers the way that some of the others are.)
...that being easy to remember because it was the same digits as the altitude of geosynchronous orbit ...
That's serious indication of geekery there! And yes, I think the two mantissae are close.
For some reason, Avogadro is rather close to the top of the random-access heap for me. I wonder why... There was a time when I was doing ions as function of current, but that's long ago, I can't seem to recall having used it for anything in a long time.
Boltzmann is something I use all the time, and it is a stand-alone value for me. Probably someone might derive it from the first principles; not me, though.
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Correctly, the slug, not the pound, is the unit of mass in the fps system. It's the amount of mass which one pound of force will accelerate at one foot per second per second.
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I think the acceleration = one pound/sec^2
Application of a pound of force gives 1 slug or the equivalent of 32 pounds of mass per second^2.
My memory for this stuff isn't what it used to be.
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(I could say something about a system of units where there are multiples of 12, 16, 8, 4, 3, and things that are not multiples but something elses, but those are units of currency, not units of physics, and I shall leave the whole imperial measurement system alone just remarking that the imperial and colonial pound and pint are not the same just to confuse us modern metric morons.)
(no subject)
As for the rest of your comment, there are several reasons I strongly prefer the metric system if I'm going to need to do any calculations.
It's not just the dozens and sixteens; it's also the downright wonky constants you wind up with as a result. In mks some textbooks even round g off to 10 for end-of-chapter problems, and the only pain-in-the-butt conversion constant I remember having to deal with was when converting Joules to calories. (Unless I'm forgetting something involving coulombs.) Despite having been raised in fps and living in a culture that continues to use it most of the time, I really don't want to do any math or science in fps. Meters, kilograms, Newtons, Kelvins, and liters for me, thank you very much.
(Though there is something to be said for the number of convenient factors that go into Babylonian base-60 measurement systems, as well...)
(Doh! Okay, I do remember one other oddball constant: liters/mole @ STP. But ISTR that being easy to remember because it was the same digits as the altitude of geosynchronous orbit with a different exponent, right? And then there's G and Avogadro's number, but those aren't everyday outside-the-lab numbers the way that some of the others are.)
(no subject)
That's serious indication of geekery there! And yes, I think the two mantissae are close.
For some reason, Avogadro is rather close to the top of the random-access heap for me. I wonder why... There was a time when I was doing ions as function of current, but that's long ago, I can't seem to recall having used it for anything in a long time.
Boltzmann is something I use all the time, and it is a stand-alone value for me. Probably someone might derive it from the first principles; not me, though.
(no subject)