Talk:Slug (unit)/Archive 1

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Archive 1

typography

What the hell does "14.593 90 kg" mean? Is this 1.59390 kg? 14,593.90 kg? I'm a reasonably informed reader and I can't parse this. Anyone have an explanation for this format? ericg ✈ 21:24, 16 November 2006 (UTC)

i think this means 14.59390Kg, or rounded to 14.59Kg. =)

It's the correct way of writing 14.59390 kg in the SI metric system. Full stops can be used as decimal points (though commas are recommended) and spaces are used as the digit grouping symbol, in groups of three, to the left and right of the decimal point. See the definitions of SI in the International Standards Organization documents ISO-31 and ISO 1000.

Explanation: The US and the USA use a full stop (US: period) as the decimal point symbol and they use the comma as the digit grouping symbol. Other countries, including France, the founder country of the metric system, do exactly the opposite.

1.234 means "one point two three four" to an Englishman and "one thousand two hundred and thirty four" to a Frenchman.

So, to avoid confusion, SI specifies that the space (ideally a printer's "thin space" if possible) must be used as the digit grouping symbol. It also says (quite reasonably) that you can group digits to the right of the decimal point.

Sadly, the Wikipedia Manual of Style says that numbers attached to SI units must not be written in the style mandated by the documents that define the SI system, but instead the customary US-UK rules must be applied to SI units. (Which I think is daft.) Hope that helps. Blaise 17:23, 29 June 2007 (UTC)

Units

The units wear incorrect on this page, it appears in the history that they were correct and the page was changed at some point. I changed them back, and used the Math formatting so it is easier to see the relationship. I'm not sure why there is a controversy as to the units, but for slugs to be consistent with my fluid mechanics text book this change was necessary.Zath42 (talk) 22:27, 17 February 2008 (UTC)

Usage

Slugs were used in UK aerodynamics text books before metrication. I seem to remember them being used in formulas incorporating the kinematic viscosity of air. Ian Dunster (talk) 20:55, 30 June 2008 (UTC)

Do real slugs exist

and what are they made of, what is the easiest material to make a slug from. ie what metal has the right density to be a manageable size when it has exactly that mass? --81.105.242.11 (talk) 15:41, 25 September 2008 (UTC)

The slug is similar to the kilogram. Both are units of measure, specifically mass units. -Fnlayson (talk) 16:54, 25 September 2008 (UTC)
On the surface of the earth its common to measure weight in terms of the pound (force). I'm not aware of any available off the shelf, but you could calibrate your scales to read in slug. Its just a unit of measure (as previously stated). There's no such thing as a real kilogram either (though the base units of 1.0 kilogram and 1.0 pound are likely each based on the weights of different obscure objects in history, such as the weight of King George's left shoe, though probably not that exactly). The easiest material to make a manageable slug mass from would be lead since it needs to be the equivalent of about 14 kg. Alternatively, a cube of steel with sides 120 mm long would be about one slug (based on density of steel being 7850 kg/m3). — Preceding unsigned comment added by 119.18.0.134 (talk) 01:47, 5 October 2011 (UTC)

Definitions

The article would be much clearer if there were definitions, especially for the distinction between g and gc. Can someone help with this please? SciberDoc (talk) 08:50, 20 March 2009 (UTC)

I've used slugs for years and never concerned myself with gc. Its not relevent if you just use ft, pound, slug and seconds (converting to/from other units as necessary). I actually never even heard of pound mass until I came across it on Wikipedia (I'm yet to be convinced that its even a real unit of measure, since its basically equivalent to a pound force on the earth's surface - so why not just use pound force). — Preceding unsigned comment added by 203.129.23.146 (talk) 06:22, 5 October 2011 (UTC)

Big thanks to Hqb

Hqb is the first person to reference the etymology of the word and mathematical term “slug”. Despite my suspicions and the contradictory reference of a 1928 text book (not referenced), I believe Hqb has earned a well deserves round of applause. Greg Glover (talk) 21:53, 31 July 2010 (UTC)

Chuckle.

The unit slinch (a portmanteau of the words slug and inch [5]) is an inch version of the slug (1 slinch = 1 lbf·sec2/in = 12 slugs).

Thus setting us up for a header on How the Slinch Stole Newton-mass. His birthday is Dec. 25, you know. SBHarris 22:10, 31 July 2010 (UTC)

Inconsistency

The article states "The slug is part of a subset of units known as the gravitational foot-pound-second system (FPS)" and then in the table shows the slug as being part of the FPS engineering system.

From one of my aeronautics textbooks, "at the surface of the earth, an object with a mass of 1.00 kg weighs 9.8 N or 2.205 lb, and an object with a mass of 1.00 slug weighs 32.17 lb or 143.1 N". The textbook is: Shevell, R.S. (1989) "Fundamentals of Flight", 2nd Ed, Prentice-Hall. The quoted statement is on page xix in the section titled "Conversion Factors between SI Units and English Units".

All Wikipedia articles featuring anything to do with pounds as something to do with weight seem to be lacking credibility because of an apparent widespread misunderstanding of what a pound is and inconsistency in use of specific system of units. In the Slug (mass) article, units from FPS engineering and FPS gravitational systems are mixed in the same equations.

Its unfortunate that there are (too many) different types of "pound" as a physical unit, which is probably why the world will eventually abandon the English system altogether in favour of the clearer SI units (kg, N). Only industries with substantial legacy data in English units (such as aerospace) will be forced to retain them until such legacy data can be converted. 203.129.23.146 (talk) 04:08, 5 June 2011 (UTC)

Your changes were incorrect. I have reverted them. Rracecarr (talk) 22:34, 17 February 2008 (UTC)
The units for slugs work out just fine using F = ma. So the units are [lbf] = [lbf-s2/ft]*[ft/s2] = [lbf]. -Fnlayson (talk) 22:48, 17 February 2008 (UTC)
It was a typo in my fluids book, not repeated later in the book...Zath42 (talk) 08:38, 26 February 2008 (UTC)

Mass

How can its mass depend on g? Surely it must be independent of it?

What is the mass of one cubic foot of water? W = 62.4 lbs per cubic foot, g = 32.2 ft/s2

mass = W/g = 62.4 lbs/ft3 x [1/(32.2 ft/s2)] = 1.94 (lbs s2)/(ft4)

Please, tell me if I am right. If not, what is wrong.

This gives you the density of water at 1.94 (slugs)/(ft.^3) —Preceding unsigned comment added by 76.171.46.46 (talk) 02:48, 11 August 2008 (UTC)

It has units of force/acceleration, and the units of force are mass*acceleration, so the units of slug are (mass*acceleration)/acceleration, with the accelerations cancelling to leave mass. If used correctly, the slug is independent of gravity. You say the weight of one cubic foot of water is 62.4 pound but then add "/ft3" in your equation. A weight is just a weight (pound). What you are trying to say in the end is that the density of water is 1.94 slug/ft3, which is what you've got. A slug is bigger than a kg and a ft is smaller than a meter, so its hard to compare 1000 kg/m3 with 1.94 slug/ft3 without crunching the numbers. — Preceding unsigned comment added by 119.18.0.134 (talk) 02:05, 5 October 2011 (UTC)

According to the 5th reference of the article, the slug described by A.M. Worthington has units of mass, not inertia as claimed in the article. A careful reading reveals that the author is referring to a unit moment of inertia produced by one slug at one foot, not a unit moment of inertia of one slug. Specifically, on page 26 "the unit of mass is 1 slug = 32 lbs. (nearly)". In light of this, I am removing the clause 'as a unit of inertia' and the associated link. 72.131.117.42 (talk) 00:45, 23 January 2013 (UTC)

That looks correct about the source. However, inertia and moment of inertia are 2 different things. Mass is an inertia. -Fnlayson (talk) 01:25, 23 January 2013 (UTC)

Seconds abbrev.

This may seem as nitpicking, but in English units, seconds are abbreviated as "sec" rather than "s". So, for instance, shouldn't the acceleration table read: ft/sec^2 rather than ft/s^2? All engineering textbooks I've seen have made the distinction of using "sec" in English, vs. "s" in Metric. Silver bow (talk) 20:22, 25 February 2009 (UTC)

Both "sec" and "s" are acceptable abbreviations. My engineering texts use "s" and sometimes "sec". Wikipedia policy does not have specify one or the other. -Fnlayson (talk) 20:56, 25 February 2009 (UTC)

Metric slug

There is no metric slug, (N)Newtons are for that, the slug is the imperial version of Newton. It is an invention of american who doesn't understand Newtons. This 9.80665 is the gravitional constant. So for people out of the US :"Don't use kgf or metric slug, people will laught at you." —The preceding unsigned comment was added by 209.161.248.198 (talk • contribs).

I don’t know whether the term “metric slug” is or rather was indeed used in the English-speaking technical world, but hyl and TME were in fact defined by standards bodies, but are long deprecated—so are all units that enclose (gravitational) constants, such as the kilopond / kilogram-force.
I am not sure whether the hyl was a cm-g-s or a m-kg-s unit, though. Christoph Päper 15:28, 15 February 2007 (UTC)
The slug is not the imperial version of the Newton. pound-force is the equivalent unit for a Newton. The slug is the equivalent unit to Kilogram in that it represents a mass that when multiplied by the local acceleration due to gravity yields the weight of the object. --Stepbot (talk) 20:39, 5 December 2015 (UTC)

I want to delete the pop culture reference. I don't see how it is relevant to this article. I hope I want be bugged by a revert bot. —Preceding unsigned comment added by 207.43.190.31 (talk) 22:50, 6 January 2008 (UTC)

Metric slug-like units as follows. 1. glug = gramf s² / cm [cgs], hyl = par = TME = mug = kgf s² / m [MKS]. All of these units appear in dictionaries of weights and measures, in period books lile Hvistendahl's "Engineering Units". SI does not have this, although metric does.--Wendy.krieger (talk) 07:59, 19 February 2011 (UTC)

A "metric slug" is about 14 kg. 203.129.23.146 (talk) 01:30, 28 July 2013 (UTC)

Details on gc

http://www.me.mtu.edu/~jstallen/courses/MEEM4200/lectures/energy_intro/Review_unit_systems.pdf — Preceding unsigned comment added by Jitenk87 (talk • contribs) 16:32, 5 December 2011 (UTC)

History

The slug also has significant heritage in the aerospace industry if anyone's looking for a homework exercise :) — Preceding unsigned comment added by 203.129.23.146 (talk) 10:42, 25 July 2013 (UTC)

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