Talk:Slug (unit)

Blob

I removed this definition which was added last October unreferenced by an anonymous user:

The unit blob is the inch version of slugs (1 lb_f·s²/in).

SockPuppetForTomruen (talk) 20:24, 12 April 2008 (UTC)

http://www.designofmachinery.com/MD/ for blobs, also 'slinch' is a gross of blobs, not the inch version of slugs (whoever added it had the conversion wrong, it would have to be 1/12 a slug not 12 slugs)

12 slugs = 1 slinch

1 slugs = 1/12 slinch

, this is because

$1[slug]=1{\cfrac {[(lbf)(s^{2})]}{[ft]}}$

and

$1[slinch]=1{\cfrac {[(lbf)(s^{2})]}{[in]}}$

and since 1 foot = 12 inches

$1[slug]=1{\cfrac {[(lbf)(s^{2})]}{[ft]}}=1{\cfrac {[(lbf)(s^{2})]}{12[in]}}$

do some algebra (multiply all sides by 12) to get

$12[slug]=12{\cfrac {[(lbf)(s^{2})]}{[ft]}}=1{\cfrac {[(lbf)(s^{2})]}{[in]}}$

I don't understand the blob. Is there only that one source for the information on the blob? A Google search is useless as there are too many movies or other things named blob. Could 12 blobs = 1 slug(1/12 slugs = 1 blob) as you where saying is the cases of the slinch? Is that the difference between the slinch and the blob?R00m c (talk) 03:29, 16 April 2008 (UTC)

yes, they are the same. —Preceding unsigned comment added by 130.215.238.136 (talk) 07:03, 16 April 2008 (UTC)

I removed the statement about the blob because it is not a commonly accepted term. From the reference:

It is unfortunate that the mass unit in the ips system has never been given a name such as the term slug used for mass in the fps system. The author boldly suggests (with tongue only slightly in cheek) that this unit of mass in the ips system be called a blob(bl) to distinguish it more clearly fron the slug (sl)...

As this is the only source, and the author is merely suggesting the use of the term, I don't think it qualifies as a fact.Djd sd (talk) 23:57, 23 May 2010 (UTC)

Page 21 of Shigley states (regarding the "unit of mass in the ips gravitational system"), "The mass unit lbf.s²/in has no official name.". Shigley also states "there is no abbreviation for slug". — Preceding unsigned comment added by 119.18.0.134 (talk) 01:29, 5 October 2011 (UTC)

No one has ever used "blob" in this context. This needs to be removed because the topic is confusing enough without this misinformation. — Preceding unsigned comment added by 66.35.45.68 (talk) 14:45, 9 September 2015 (UTC)

References

Relevance

How relevant is that unit slug today, and where and for what business? When there is written about an Australian act of 1960 (no citation!) then this is 53 years ago and Australia is metrificated since 20 years. So slug doesn't seem to be a legal unit for mass in Australia any more. Its coining in the 19th century and the 85 year old textbook paragraph doesn't make it youngeror more relevant.

Since Einstein's claim of 1907, that there is no difference between inert masses and gravitational masses (and energy), a special unit for inertia is not necessary. (Albert Einstein, Jahrbuch der Radioaktivität 1907, p443 + p462, "Über das Relativitätsprinzip und die aus demselben gezogenen Folgerungen")

Is there any relevant modern publication in which a producer, trader or scientist expresses the mass of e.g. a car, a bag of potatoes, an engine or a planet by its intertia in slug?

If there isn't any, it should be mentioned in the article that slug is an old, expired unit out of use and relevance. Its use in concurrence to the pound is over-subtle and obsolet (if one still insists to express something in imperial units). --46.115.49.76 (talk) 15:23, 24 January 2013 (UTC)

Engineering Textbooks still use it in the U.S. Example: Engineering Mechanics: Statics, Bedford and Fowler 1999 (and probably subsequent). This is by no means an obsolete unit. 130.76.96.156 (talk) 21:51, 25 January 2013 (UTC)

Slug is relevant as it is the only non-ambiguous and coherent unit of mass in the fps system of units. It is widely used in engineering (particularly aerospace). 203.129.23.146 (talk) 11:49, 5 July 2013 (UTC)

From my experience, slugs are mostly obsolete, but they do still occasionally pop up from time to time. For example, I ended up on this page after having to look up the density of water in slugs/ft3 (1.94 for anyone curious) to plug it into an equation in a building code. However, it is far more common to see pounds-mass (lbm) used than slugs, in both industry and academia. 108.52.118.74 (talk) 22:31, 29 September 2016 (UTC)

Slug value

I reverted the recent edit because the original seems to be correct. See http://sizes.com/units/slug.htm and the following calculation.

1 slug = mass that accelerates at 1 ft/s² under 1 pound force = F/a = 1 lb_F / (1 ft/s²)

1 lb_F = m g = g in ft/s²

1 foot = 0.3048 m exactly (Foot (unit))

1 g = 9.80665 m/s² exactly (Standard gravity)

1 slug = 9.80665/0.3048 = 32.17404856 pounds mass approx

Johnuniq (talk) 03:52, 1 November 2015 (UTC)

lb, lbm and lbf

The international standard symbol for the avoirdupois pound is lb, not lbm. In what sense is it clearer to use a non-standard symbol? Dondervogel 2 (talk) 19:35, 11 December 2016 (UTC)

... and while I'm on the subject the international symbol for the pound force is lbf, not lb_F. I will correct that next. Dondervogel 2 (talk) 20:08, 11 December 2016 (UTC)

In general, pound can be taken as either pound-force or pound-mass. Labeling the mass version as pound-mass avoids confusion. Wikipedia is for general audiences, not just science and technical ones. -Fnlayson (talk) 20:11, 11 December 2016 (UTC)

I have never seen them distinguished in this way outside Wikipedia. Are there reliable references that do so? Dondervogel 2 (talk) 20:27, 11 December 2016 (UTC)

• I have several engineering text books that use pound for pound-force and at least one that uses pound for pound-mass. This is largely the authors' conventions and not an official convention. -Fnlayson (talk) 20:42, 11 December 2016 (UTC)

OK. I have two follow on questions.

• How do those text books define the unit "pound" when used as a unit of mass?
• What symbol do they use for that unit? Dondervogel 2

Dondervogel 2 (talk) 22:27, 11 December 2016 (UTC)

• Ones like the Shigley and Mischke book (ref #2 in article), use lb-s²/ft, i.e slug for mass, along with corresponding SI unit, kg. That's all I have. If you don't believe me, whatever. -Fnlayson (talk) 02:06, 12 December 2016 (UTC)

I am willing to believe that different symbols are used for a pound of mass outside wikipedia, even though I have not seen these myself. What I question is your assertion that 'lbm' or 'lb_m' is a more appropriate symbol for Wikipedia than the international standard symbol, 'lb'. I asked for a reliable source because that would permit us to discuss the relative merits of the different sources vs the international standard. Dondervogel 2 (talk) 12:32, 12 December 2016 (UTC)

See also ongoing discussion at mosnum. Dondervogel 2 (talk) 20:59, 13 December 2016 (UTC)

Physicists may not like it, but the kgf creeps into engineering books from time to time. Should we therefore insist on using kg_m to disambiguate? Since that is a rhetorical question, why therefore would Wiki invent a lb_m symbol when lb has been used for centuries. Martin of Sheffield (talk) 23:02, 13 December 2016 (UTC)

Yes, as a unit for weight. -Fnlayson (talk) 03:10, 14 December 2016 (UTC)

You seem to be arguing for the use of lb with two different meanings, sometimes for mass and sometimes for weight. Do I understand correctly? Dondervogel 2 (talk) 08:17, 14 December 2016 (UTC)

... and by the way, it has been proposed to hold the discussion centrally, at one of the project pages. I do not have time to start such a discussion, and would not know which project pages are relevant. Instead I propose a centralized discussion at mosnum. Dondervogel 2 (talk) 08:27, 14 December 2016 (UTC)

• As I stated above that pound is sometimes used for pound-force or pound-mass depending on context. I was not replying to any of your posts. You can always ignore comments. -Fnlayson (talk) 12:22, 14 December 2016 (UTC)

As lbf is used for pound-force (per IEEE standard), I see no benefit in introducing lbm - use of non-standard symbols leads to unnecessary ambiguity. On the other hand the template does use lbm and lbf, so either we edit the template or we need to define 'lbm'. As a stop-gap measure I will add a link from lbm to pound mass. Dondervogel 2 (talk) 18:45, 30 December 2016 (UTC)

References

@Dicklyon, Fnlayson: I add the link. Is that sufficient to explain what is meant by lbm? Dondervogel 2 (talk) 18:55, 30 December 2016 (UTC)

• Fine with me. -Fnlayson (talk) 20:32, 30 December 2016 (UTC)

Choice of parenthetical disambiguation of title

The parenthetical disambiguation should be a generic class/context/subject/adjective, and not a noun. I seem to remember that the context should be as broad as possible to, i.e. giving only just sufficient context to disambiguate. Currently, the title is "Slug (mass)", which seems to be in violation of pretty much every guideline here. There seem to be a large number of similar articles about units of measurement that are disambiguated with "(unit)", e.g., Atmosphere (unit), Barn (unit), Bar (unit), Chain (unit), Foot (unit), Gauss (unit), Gal (unit), Gray (unit), hartley (unit), henry (unit), Knot (unit), Lumen (unit), Mole (unit), nat (unit), shannon (unit), ... There are examples where more specific disambiguation is needed, such as Pound (mass) and Pound (force), which are both units. Perhaps we should rename this article to "Slug (unit)"? —Quondum 02:56, 8 October 2017 (UTC)

I agree. Slug (unit) is a better title than Slug (mass). Dondervogel 2 (talk) 08:04, 8 October 2017 (UTC)