User talk:Kernigh/pound
Some comments by Metric1000[edit source]
No standards agency maintains one definition of a pound for commerce and another for everything else.
Pounds are defined as units of mass exactly equal to 0.45359237 kg all around the world, since a 1959 agreement among the national standards agencies of the United States, Canada, the United Kingdom, South Africa, Australia, and New Zealand. This definition has also officially been adopted in other places such as Ireland.
Of course, that redefinition made no change whatsoever in what quantity (as we use that term for weights and measures) is represented by a pound. It already was a unit of mass. In fact, in the United States, it had already been defined as a slightly different exact fraction of a kilogram for 66 years before that common, international agreement was put into use.
Slugs are a little used, 20th century invention, something that didn't appear in physics textbooks before 1940 and which have since disappeared from most of them, along with the rest of the English units.
So yes, pounds-force do also exist. Before the 20th century, they were never well-defined units, though they had already been used in low-precision applications for a couple of centuries before then. For example, in the boiler of a locomotive, it doesn't really matter much whether the actual accurate value of the gauge pressure is 450 of some well-defined unit, or 475 of some well-defined unit; using a pound-force based on whatever the force on a mass of one pound, under the influence of the local gravitational field, isn't going to matter in these low-precision applications.
Slugs, of course, did not exist when the United States first redefined the pound as an exact fraction of a kilogram.
What, exactly, is a poundal? It is part of a coherent foot-pound-second system, the absolute fps system, which is older than the gravitational fps system including the slug. The poundal dates back to 1879, at least.
I'll even tell you what it is, so you don't have to look it up (unless you don't understand me or don't believe me). The poundal is a derived unit of force. It is the force which will accelerate the base unit of mass in that system at a rate of one foot per second squared. Now your homework, a simple fill in the blank:
- The base unit of mass in this oldest fps system is the _______________.
HINT: It is the "p" in this "fps" system.
Metric1000 11:05, 24 October 2005 (UTC)
ditch the units[edit source]
This is silly. The use of unnecessary units is bad, even if we didn't have to deal with poundforce and such. Do like this:
People on Endor are pulled down with 1.23456 times as much force as they would be on Earth.
That's the number you need if you want to take your weight, in any system of units, and multiply it by something to get a feel for the difference. It works for any loose idea of stones, pounds, newtons, grams, slugs, etc.
If you decide to get all scientific, you can argue about units for acceleration, not force. Acceleration of gravity on Earth is 20/7 rods/microfortnight/microfortnight.