Talk:Pound (force)

pound-force

It seem interesting to define a quantity that can be directly measured in terms of a quantity that cannot be directly measured and may just be a mathematical convenance.--208.54.14.122 (talk) 08:35, 3 July 2010 (UTC)

PatrickandBrenda 03:10, 11 August 2007 (UTC) In the United States, which is the primary user of the pound-force, the pound-force is almost universal in its application to industry and throughout daily life. I challenge anyone to reasonably argue

"In most daily contexts in the United States, the term “pound” refers unambiguously to a unit of force. Bathroom scales intrinsically display weight or force. An important note, all scales read force as only a balance such as used in a doctor's office can determine mass. A truck carrying one-thousand pounds of wood refers to the weight or force the wood exerts on the truck. At a local grocery store, one pound of meat will refer to the force or weight of the meat, and may even be weighed using a scale at the meat counter..."

I also challenge people who oppose this to present common everyday uses or pound-mass (other than niche industry uses).

The pound force has historically and continues to be today the primary use of the word "pound." As a Senior Mechanical Engineer for Westinghouse Electric Co. (Other employers include Terex Corp. and Emerson Process Management among others) I have never encounter a company (outside steam power plant designers) that ever (used in the literal sense) use pound-mass.

Very well. Look at a sack of flour in the supermarket. It may say "net weight 5 lb". This amount is given in mass, not only by convention, but legally. If it were other than 5 * 453.59237 g (within tolerances), the seller would be in violation of the law. It would be no defense to say they weighed it at the top of a high mountain, thus its gravitational force was less.

See below and my update to pound mass.

Bathroom scales measure weight by force. It's true. What are they reporting? Mass. Their purpose is to tell you how much mass you have. If you move the scale to various elevations, granted, its accuracy will suffer, because it wasn't designed any better. But notice that alongside the pound amounts are kilograms. Why is that? Because it measures mass.

Incorrect, see below. It reports force, which by definition is the same as pounds mass. But it is of course a force. As you so astutely report, it will also report something different in space. And scale makers have not interest in trying to do something as difficult as reporting mass. Hence, the pound they display is to indicate force. Trying calling a scale maker, request a technical question. They will direct you to an engineer who designs them and decides what it is to display. They will tell it means force. Honestly! 66.41.157.69 02:07, 12 August 2007 (UTC)

"At a local grocery store, one pound of meat will refer to the force or weight of the meat, and may even be weighed using a scale at the meat counter..." - absolutely false. It refers to the mass. The means of measurement is irrelevant - the fact communicated by the statement "your meat weighs two pounds" is: "you have two pounds (mass) of meat". If you try to define something by the method by which it was measured, you quickly run into absurdities. For example, on some spacecraft are devices for measuring the mass of astronauts. They work because when a certain force is applied to the astronaut, the astronaut begins to move, but resists. So, if the method of measuring defines the outcome, what property of the astronaut is being measured? I could take my pick - force, inertia, or mass. Except we don't have to guess. It's mass. Even though the measurement involves force.

This again is incorrect. See below.

Your knowledge of physics in this case is of great concern. If an astronaut is accelerated to create a measurable outcome that would of course be force (f=ma, where the astronaut of some mass is accelerated and therefore the result is force). The mass would have to be calculated secondarily based on what acceleration they used. (Keep in mind he or she would not be on earth so we can not assume 32.2 ft/s^2.) Then to find the derived unit of pounds mass you must use the gravitational constant, as it is required (only) for pounds mass. Where of course g is simply a constant added to compensate for a unit cancellation when this derived unit is used. This is the only way this can be determined. The force applied to the astronaut is of course equal and opposite to the force he or she press against the scale while causing a proportional acceleration. As you can see the force is of course measured on this scale (you can't really mass on a balance in space.) And therefore mass is calculated, not measured. 66.41.157.69 02:07, 12 August 2007 (UTC)

I will try to make the point more clearly. You said above that a scale reports force, and therefore a pound is force. My basis of my rebuttal is that the means of measuring a quantity do not define what is measured, and therefore you're incorrect. Take for example a modern bathroom scale which measures a person's weight via pressure piezoelectric devices. The person's weight (a force) compresses the scale, producing an electric current. The current is processed and the result displayed. If we were to use your method, the user might report that he weighs 190 pounds "of voltage" - clearly an absurd outcome. The solution to this is to realize that the device is communicating a result whose means of measurement is irrelevant. --Yath 03:42, 12 August 2007 (UTC)

All this is not to say that the pound isn't a unit of force. It is. But it depends on context. I've shown you some contexts where it's a unit of mass; there are many others where it's a unit of force. The points are: 1) it's more often a unit of mass. 2) writers of encyclopedias don't get to choose which use is more important. We just observe and report. And if we don't like the way people use terms, tough. --Yath 06:02, 11 August 2007 (UTC)

Wrong an encyclopedia is not to follow the crowd, but to report the truth even if you don't like it. See my contributions on pound mass for problems with your arguments.

Unfortunately, "In this you are completely wrong Yath. While 5 lb of flour in a grocery store, by defintion is both 5 pounds force as well as 5 pounds mass. The use referred to is force. The "legal" basis that you refer to I would like you to quote specifically from law text. The use of pounds force in no way is illegal, as the difference in weight between the bottom of the sea and the top of Everest is inconsequential. I have worked for and with mass manufacturers of materials such as Cargill and Campbell's and I can tell you unequivocally the unit used is force. And to my knowledge they have never been (or at least never successfully) sued for using force. Like all others they use scales (I can't emphasis this enough), which can only determine force. They are never specially calibrated for elevation. They are calibrated at a NIST qualified facility and then sent back to the facility for use."

Again what technical basis is your knowledge based on? Do you work for NIST, a professor, any number of other expert positions on this topic? 66.41.157.69 02:07, 12 August 2007 (UTC)

No, none. P.S. - it will be easier to follow this conversation if you sign each of your paragraphs.

I suppose the weighing-things-on-a-mountain example was a poor one, because we've gotten caught up on the inconsequentiality of the difference in gravity while that really wasn't the point. You're right, it is unlikely for anyone to be sued, because the difference in measurement would be beneath the tolerances. At any rate, to quote U.S. law that is relevant:

Commercial units of weight and measure in common use are based on the yard and the avoirdupois pound.[...]1 pound (avoirdupois)=0.453 592 37 kilogram US CODE Title 15,205

This demonstrates that items sold "by the pound" are sold by mass. It's further reinforced by the inclusion of SI units on packaging. --Yath 03:42, 12 August 2007 (UTC)

Well, I think you are still wrong on the scale. :) Voltage is directly proportional to force, and it is calibrated as such, by applying a known force. Scales will always only measure force. Although people may equate it to whatever they please. As for commerce, I stand corrected! I wouldn't have believed it until I read in law. Indeed, in 1993 NIST changed their definition of "weight" (in reference to commerce anyway) to mean "mass". I added a section to the pound-mass article to describe my references and research. I would have expected more from NIST than to bow to Politicians, but so it go. Can't bit the hand that feeds you.PatrickandBrenda 18:28, 13 August 2007 (UTC)

Careful here. The archetypal scales are pan balances. Pan balances do not measure force, they compare masses; and do not require adjustment for local g-force, so they do not measure forces. The earliest definition of the pound was in London for use with pan balances. So the pound was first and foremost a measure of mass. And the fact that this is so matters with very precious materials- the g varies over the surface of the earth, and the weight varies and spring balances need adjustment to correct the variation of weight to give an accurate measure of the mass of these products.WolfKeeper 18:50, 13 August 2007 (UTC)

I'm a little out of my league on this topic, but I believe scale actually comes from scalepan. The pan used on those ancient balances. So, I'm not sure scale would have been the proper term even then. Scale is also a word for bowl or cup. I could image that is how a single plate you put something on became known as a scale. Either way, for a long period people did not differentiate between mass and force, because they did not know the difference.PatrickandBrenda 21:51, 13 August 2007 (UTC)

I think that the concept of force didn't even appear until Newton, about 3 centuries later, so yeah. And without a concept of force, the original concept was much closer to mass than weight, since weight is a force.WolfKeeper 21:59, 13 August 2007 (UTC)

Right and wrong here all at the same time. Force was not explicitly differentiated for a long time, because everything was force. No one had an conception of an innate property we now realize and call mass. Only that which could be experienced (force) was understood. So, the world worked in force (although they were actually quantifying it through mass). —Preceding unsigned comment added by 147.72.234.5 (talk) 21:51, 17 September 2008 (UTC)

But the pound was defined for a pan balance- pan balances compare mass. They do not measure force. If you carry a pound weight around to places where the gravity varies, one pound is still one pound of mass. But the weight (a force) varies.- (User) Wolfkeeper (Talk) 22:21, 17 September 2008 (UTC)

I think "scale" probably suffers the same issues as pound (most assuredly on the same timeline), and is best considered after the differentiation became clear and accepted. =) But I believe correct use of scale is to weigh, which implies force and to mass to find mass. (such as in mass balance or to mass a lead slug) It is often misused in SI countries, but in my opinion that's to be expected when someone goes from weighing 200 lb(f) to being told they are 91 kg, a by product or switching from a force-based system to mass-based. One just assumes to same usage of having been "weighed". And vice versa for someone having gone from a regular bathroom scale to a balance at a doctors office. Dr. after all studied biology and probably carry little about physics or whether they are weighing or massing. Just my thoughts there. PatrickandBrenda 21:51, 13 August 2007 (UTC)

Actually no, to my recollection prevailing thought before Newton and his concept of gravitation had nothing to do with mass as you are viewing it. And it could be at least as easily asserted it actually was closer to force than mass. To the point, prevailing theory of the time was that everything was comprised of "elements"; namely earth, water, fire, and wind (or air). Each could be determined by its naturally tendency to rise above the previous. Wood for example, although substantially earth, floated; and this made sense by the theory because wood contained a lot of fire, which was lighter than water. As was evidenced by burning it. Their experience was of a person living in a physical world dominated by gravity and force, not abstract. An ox could plow by pulling hard against a yoke. And enough wood lets you float stone down a river. Too much stone crushed a cart under its weight. This is why many historically systems are force-based. Their weights of course had mass. It's not possible to have been massless. But force is how we sense the physically world. We can't sense (in the literal sense) mass, we can only feel the force it creates. PatrickandBrenda 02:29, 14 August 2007 (UTC)

Until Newton 'force' was not well defined. The idea of mass was roughly equivalent to heft, and was measure by a pan balance (which compares mass of an object against standard masses).- (User) Wolfkeeper (Talk) 22:21, 17 September 2008 (UTC)

I think a lot of this discussion is missing the point about the pound-f in the system of units. It is entirely true that people have used force and mass interchangeably in the popular setting because a pound of mass produces a pound of force in Earth's gravity where most people experience it. However, there are other units to be considered here. What about the FPS units for energy? -- ft-lbs. Energy must be a distance multiplied by a force, not by a mass. So a pound-mass may be the common and legal/commercial definition, but for the rest of the system to be coherent, lb-f needs to be used. ArkianNWM (talk) 19:37, 24 April 2009 (UTC)

energy = Force x length = foot.pound. power = foot.pound / second, 550 ft lb/s = hp, 75 kg m/s = metric horsepower. Pressure = pounds per square inch, viscosity pounds-second/sq inch. mass (by f=ma) slug = lb.s²/ft, amount of substance slug-mol = (lb.s²/ft)-mol. Coherence is an add-on to a system. One can multiply and divide units without 'coherence', eg metric km/h vs coherent m/s. --Wendy.krieger (talk) 07:29, 1 October 2011 (UTC)

If your measurement uncertainty is more than the variation of g around the earth (or, probably country), one can mostly ignore the difference. Note that at high accuracy, one also must include buoyancy to properly measure mass, even on a balance. If grocery story digital scales are calibrated with standard masses, and since g doesn't tend to change (within tolerance) at a fixed location, it should be close enough. The confusion of pound(mass) vs. pound(force) is that in most cases the value is close enough. No-one will confuse kg and N. Gah4 (talk) 11:10, 9 February 2019 (UTC)

From Pound (mass): Usage of the unqualified term pound reflects the historical conflation of mass and weight. For common usage, one can ignore the difference. Modern grocery store scales, likely with a strain-gauge sensor, measure to 0.01 lb. I believe up to the highest mountaintop, at least as high as you find a store, the difference is within the uncertainty. Gah4 (talk) 20:45, 1 August 2019 (UTC)

For more fun, note the units commonly used for specific impulse. It is most often given as thrust/(weight/time). (Weight is mass times standard g.) The thrust of a rocket engine divided by the rate at which fuel and oxidizer are consumed, by weight. For a jet engine, just fuel, not the weight of the air used. This results in a unit of seconds, and the same value in English or SI units. For rocket engines, multiplied by standard g, it is related to the exhaust velocity. For jet engines, it has no relation to any actual velocity. Gah4 (talk) 20:55, 1 August 2019 (UTC)

pound vs. slug

Will you guys stop this edit warring and find a cite to settle the matter? edit, revert... It's not like this is a matter of opinion or anything. --Yath 07:41, 19 August 2007 (UTC)

I don't see reverting patent nonsense as edit warring. You don't have to look very far for a ref--try slug (mass). This statement:

"One pound-force is the force equivalent to that exerted on a mass of one slug accelerated by gravity on the (idealized) surface of Earth or one avoirdupois pound at an acceleration of gravity divided by the universal gravitational constant."

is false. A pound (force) is the amount of force exerted by gravity on a pound (mass). That's why it's called that. The idea that the universal gravitational constant is involved is absurd. The units don't even work out. Rracecarr 15:39, 19 August 2007 (UTC)

• Nope. Both of those are right. A slug is 1 lbf divided by acceleration of gravity. It's not the universal gravitational constant. It's a constant called g_c. The formula in the second table explains the g/g_c thing. -Fnlayson 19:04, 19 August 2007 (UTC)

• Nope back atcha. The gravitational force on one slug at the Earth's surface is about 32 pounds NOT 1 pound as claimed by PatrickandBrenda. One pound of force accelerates one slug at 1 foot per second squared, not 32 feet per second squared, as the gravitational force on it would. The universal gravitational constant has nothing to do with it. It has a value of about 6.67 * 10^-11 m^3 kg^-1 s^-2, which is the same as 3.44 * 10^-8 ft^3 slug^-1 s^-2. Multiplying by that will give you an answer that's only off by a factor of about a billion. Besides, the units don't fit. What you are talking about is not the universal gravitational constant (big G) but little g, the strength of the gravitational field at the earth's surface. Rracecarr 04:37, 20 August 2007 (UTC)

Like I already said, PatrickandBrenda means gc, not G. That's not the correct engineering definition for a slug anyway. So whatever.. -Fnlayson 05:02, 20 August 2007 (UTC)

• My question is this. Why is it in the table at the bottom, the "engineering" column deals in pounds and pound-mass. But two lines above it, it talks about engineers preferring to be in the slug system? The table's wrong. I am an engineer, and though alot of schools teach pound-mass, the majority teach slugs. 130.76.32.144 15:15, 15 October 2007 (UTC)
  • They teach both or should. Thermo-fluids generally uses pound-mass, ime. While slug is used more by Mechanical systems. -Fnlayson 15:46, 15 October 2007 (UTC)

Acceleration due to gravity

The acceleration due to gravity is given to an absurd number of decimal places, given that it varies from place to place. In fact, this article generally uses too many significant digits. Even when your numbers are exact (or of arbitrary precision), it just looks bad.

Also, pound-force is the common unit, not pound-mass. Sure, you can generally get away without making a distinction, which is why some people get confused, but ask any scientist or engineer, and they will tell you that "pound"--unqualified--means pound-force. If you don't believe me, [1] —Preceding unsigned comment added by 141.219.154.178 (talk) 16:32, 14 November 2007 (UTC)

There is a standard value for g, which may or may not be close to the actual g where you are. Thus the pound(force) is the pound(mass) times the representative standard g, and divides by the value of such standard g, with its units removed. If one does physics in US units, one normally (though rarely) uses the slug-foot-second units. On the other hand, chemical engineering is done with pound(force), pound(mass), and the special constant g_c to fix things. On the third hand, one could use (and I forget who does) a pound(mass)-foot-second unit system, such that force is in pound-feet/second squared. Gah4 (talk) 11:24, 9 February 2019 (UTC)

Three approaches to mass and force units box

Someone has changed the GravEngAbs (Three approaches to mass and force units) box in the Foot-pound-second systems of units section. You can even see the error within the link: Grav = Gravitational; Eng = Engineering and Abs = Absolute! It was correct last week (21 JUL 10). Also check the English Engineering Units page it has the correct units of measure. This week the Engineering heading is switch with the Gravitationl heading. The Engineering system is non-coherent: $F=m{\tfrac {d}{t^{2}}}$. The Gravitationl system is coherent: $F=ma\,$.

Can someone fixs this error? I tried and don't know how to access the original box. Greg Glover (talk) 23:27, 27 July 2010 (UTC)

To whom it may concern,

I have removed the GravEngAbs box. I believe when it is corrected then it should be put back in. However, anyone may revert this deletion if they wish. Then there sould be more discussion. Greg Glover (talk) 16:22, 31 July 2010 (UTC)

FPS

Whom ever redirected FPS here has made a grave mistake. The pound force is only found in two of the three subsystems. The system is called the Foot-Pound-Second System or FPS.

Worthington from Great Britain (http://www.archive.org/stream/dynamicsofrotati00wortiala#page/8/mode/2up) gives two of the subsystems as, Gravitational or Engineer’s and Absolute. Obert from the United States gives the three subsystems as Technical, Engineering, and Absolute.

It is clear to me that the Foot-Pound-Second System should have its own page. A disclaimer could be made until someone finds a reference.

Further, I think this is why someone tampered with the GravEngAbs box. The three systems are, if deduced by both Worthington and Obert and applied here at Wikipedia as:

• dFt = Gravitational or (Engineer’s and Technical) System
• mdFt = Engineering System
• mdt = Absolute System

m is missing from the Gravitational System because it is equal to the slug.

F is missing from the Absolute System because it is equal to the poundal.

Otherwise:

m = mass {pound mass(1lb_m)}

d = distance {foot (1ft)}

F = Force {Pound force (1lb_f)}

t = time {second (1s)}

Greg Glover (talk) 02:21, 2 August 2010 (UTC)

Default "lb" - is it force or mass?

I see a buncha arguments about how pound is defined, as a unit of force or as a unit of mass. I happened to have learned it as a derived unit of force, defined (derived) as the force that accelerates 1 Slug at 1 ft/sec2. All very neat when one first learned the MKS system which has mass (and length and time) as the fundamental units. It is a simple matter of replacing the Kg with the Slug and the meter with the foot. Viola! Simple! That bastard unit, the ugly "pound-mass", is for people who don't really understand. It's also used for a few bad-old engineering traditions - like that awful "Specific Impulse" being expressed in "seconds" by canceling lbf with lbm for crying out loud! - lbf/(lbm/sec) = "seconds"?! (WTF?!). Anyway, lbm is really mostly just an annoyance promulgated by the ignorant, IMHO (big smiley).

But, what really matters is the current way it is defined by the real standards organizations, right? - not how it is explained by some internet engineering toolbox. My question is: "If we write "lb" or "pound" without other clarifying context, does it mean force or mass?" In the whole of my 30 year engineering career, it's meant force and that's how I've made edits. BUT! It could very well actually mean mass IF it is defined that way by the big standards organizations (not by some web page). It could also very well be defined as both, again by the big standards guys. I went with force. If we want to switch it to mass or both, I think we need to cite it well with that really good reference from those big standards orgs.

108.7.241.145 (talk) 18:38, 14 January 2011 (UTC)

The pound as the “written” word always meant the “pound mass” or weight. It is only when we forget and start substitute the “spoken” word, do things get confusing. Why? Because the spoken word for the “pound” can be shop talk. Yes, a person can be an engineer or physicist and mean force when saying the word “pound”. But the “pound” is generally know around the world as an Imperil unit of weight or pound avoirdupois.

The answer... the default "lb" is mass (weight). Greg Glover (talk) 20:23, 28 September 2011 (UTC)

I brought this up on the Pound-mass talk page, but I actually got more sense from the Science reference desk (http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Science#Pound-mass_and_pound-force.3F). It seems that as long as your on the surface of the Earth, 1.0 lbm = 1.0 lbf, but a pound-force (lbf) isn't the same as a pound (force) in engineering units, in which F=ma where F is in pounds, m is in slug and a is in ft/s^2. So a pound force isn't always a pound force. Confused much yet? What is confusing about the equations in the Pound-force article is that "1 lbf = 1 lbm . gn" isn't mathematically proper and so doesn't make a whole lot of sense (regardless of the value or units of gn). The equations in the article only make sense after the substitution to kg is made. Can anyone clear this up in the article? 203.129.23.146 (talk) 21:41, 2 June 2011 (UTC)

Let me help out a little.

Although force and weight can be mathematically equal, they are two distinct quantities:

$F=ma\,$

$={\tfrac {md}{t^{2}}}$

and

$w=mg\,$

$={\tfrac {md}{t^{2}}}$

The use of “mass” as an interchangeable word with “weight” is really an engineering colloquialism. So within the contexts of Newton's Second Law it is incorrect to say weight is equal to mass or to imply that weight is equivalent to mass:

$w=mg\equiv m$

In short you are running into engineering speak. Force is defined as “any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape.” Weight is a measurement of gravity on mass. It could also be said that what force is to weight, kinetic energy is to potential energy. Force denotes the movement of an object and weight denotes a stationary object. Force and weight are not the same.

As for 1lb_m · g_n not being mathematically proper? Your right. It is not proper because the equation was not fully reduced. Meaning: a pound force is equal to a 32.174049 pound mass being accelerated 1 foot per second squared; 1lb_f = 32.174049lb_m ft/s². The use of kg and N do help SI users Greg Glover (talk) 17:33, 28 September 2011 (UTC)

The trouble with the standards authorities is that they hold to a particular theory in deference to all others. It is similar to debating whether English is good or not based on Latin grammar. Still, the proposals by the standards authorities is one particular use, like Recieved Pronounciation is one particular dialect of English.

Weight, means indifferently mass and force. Specifically, since we have no sensation of mass, but that of force and inertia, weight is the percieved effect of force, even though it's force-of-mass. The actual word refers to measure of swung load (off a balance, weigh anchor still means to swing (raise) the anchor). One should not suppose that MKS is free of this. SI is an artificial limitation of a system that copies CGS (big dyne -> newton, big calorie = Calorie = kcal, pragilbert, etc). Units like Joule and Watt were incorporated into the MKS system: they're way older.

People who follow the 'official standard' to the letter get confused with expressions like 'psi' (pressure), 'metre' (volume), and 'cubic acre'. I've seen all of these appear in various letters to the editor. This is because the official standard does not recognise even the existance of the rules that these make sense in. 'Cubic metre' is in fact, a more precise definition than 'metre cubed', since the latter supposes that there is only one way to write M×M×M, when this is not true.

see http://os2fan2.com/gloss/pglosst.html#PGTEGUMPRODUCT where M×M×M gives 1/6 of a cube, not the full thing! --Wendy.krieger (talk) 08:10, 29 September 2011 (UTC)

Regarding w = mg == m, mathematically m x g is not equal to m unless g is unity and dimensionless, which therefore reduces to m == m (pointless). Weight is an ambiguous measure at best with no real unit unless you're an engineer where weight is universally a force (not a mass) equal to mass x gravitational acceleration (m x g). Engineers are probably among the few that don't confuse mass and weight. Force/weight is not comparable to kinetic/potential energy at all. Kinetic energy is physically different to potential energy, but weight is physically a mass multiplied by an acceleration; the only difference between force and weight is that in the case of weight we name the acceleration "gravity". Objects under the influence of forces don't have to be moving (which is the critical distinctive physical difference between kinetic and potential energy). 203.129.23.146 (talk) 13:06, 5 July 2013 (UTC)

move

The article name should be "Pound (force)." When the ambiguous term pound is used as a force, it's pronounced "pound", not "pound-force." Gerardw (talk) 10:25, 12 September 2011 (UTC)

Well, I have to disagree with you. Just because you want to be lazy or use shop talk does not change the fact the whole and complete word is “Pound force” I would agree that Pound-force is incorrect. This is the same old argument over at the Foot-pound (unit of force) page. It been moved 3 or 4 times now. The Foot-Pound force is the Foot-Pound force. Just like this page should be properly named “Pound force”. Why? Because the Pound force is the Pound force

WTF! The unit "foot pound" is a moment (akin to Newton meter), not a force! I haven't been to the foot pound article, but if it seriously calls foot pound a unit of force I don't think I want to (and Wikipedia will have lost all credibility). If foot pound is supposedly a force, I shudder to think what the pounds per square inch article says? Sheesh. 203.129.23.146 (talk) 13:15, 5 July 2013 (UTC)

Now having just disagreed with you, I would be up for a compromise. This would also bring some continuity the name usage for the “Pound”.

I propose this page be moved as you do to the "Pound (force)" page. And correct the first line to say “The Pound force (symbol: lb_f) is a unit of force in some systems of measurement; including English Engineering units and British Gravitational units.”

This would also bring this page name into continuity with the Pound (mass) page. Furthermore, if someone can move the Foot-Pound force page back to “Foot-pound (energy)” page that would be great. Greg Glover (talk) 17:58, 28 September 2011 (UTC)

I am not as much interest in being purest as I am in achieving some form of symmetry and standardization here at Wikipedia. Greg Glover (talk) 21:14, 28 September 2011 (UTC)

Edited lead as suggested and moved page. Gerardw (talk) 10:35, 30 September 2011 (UTC)

Problem is inappropriate LMT theory.

Weight is an ancient word, meaning measure (-t) of something swung (weigh, as in anchors a-weigh = swing, ie rise, the anchor). In common parlance, weight means mass, the expression of which is force. We feel the effects of force and inertia, not of mass. Weight also is used for (statistical) load.

Some parts of science have undertaken to apply gaussian LMT theory to all metrological matters, and their particular use of terminology to match. One sees all sorts of confusion as to what a 'cubic acre' might mean: it means an acre in cube (ie a volume of a cube, the face-area an acre), not an acre-cubed (ie a measure of six dimensions). Less fancifully, one sees that the vary oldest metrics have units of money. Latimer Clarke's 1890 dictionary of scientific units contains plenty of references to this, at the same ratios that were used by Mann Wilberforce's 1864 Linn-based units. This dictionary is a hard-cover work for enduring use, so one is interested to see the ratios were still in force right up to at least the great war.

Another source of endless confusion is where units are used where gaussian LMT theory (quantities have dimensions) clearly do not apply. What actually has dimensions are scales. There is a scale of force from mass (ie force-of-weight), measured in terms of mass itself (just as flux of displacement is measured in terms of the enclosed charge). There is a scale of force by F=ma, where mass and acceleration are measured in the usual units. There is also a scale of mass by this formula.

There are coherent units of mass defined by F=ma, the dimensions of which become 'MT²/L', eg fps slug, inch-pound-second (slinch), cgs (glug), mks (hyl, TME, par or mug). There are coherent units of force by F=ma fps (poundal), cgs (dyne), mks (big-dyne, newton). Some people have suggested different names for mass vs force, eg lbm vs lbf, or gram vs pond. One has even suggested that fors ought be a unit of acceleration (eg 9.80665 m/s²), so lb fors = lb × gravity.

In practice, these theories about foot-slug-second and m-kgf-s being separate systems to foot-pound-second etc, is little more than arrogance in supposing that the LMT theory is correct in all instances, and that these units are free-standing absolute scales in alternation to fps etc. Nothing is further from the truth.

The whole point of using lb vs lbf, and even units like (lb-s²/ft)-mol, is that there exists an equity between mass and force provided by gravity, and that 'lb' is indifferently mass and force (ie weight). As such, one can measure m in lb, create directly a force lb, and then create a 'reactive mass' by lb/celo = lb.s²/ft. The lbf based units are largely meaningless unless it calls down to an lbm, and that there are parallel units related in the ratio of 1:32.175 or ft/s² : gravity.

--Wendy.krieger (talk) 07:55, 29 September 2011 (UTC)

Great work, well stated! Unfortunately, I completely missed your point.

Personally, I prefer FLMT. I like to see all my variables right in front of me. My dad the aerospace engineer would of course use FLT and Newton seemed to prefer LMT.

Sorry you'll never convince me that F = m or that F and w are the same and interchangeable within the the same frame of reference; equal yes, the same no. Furthermore, F = w as E_K = E_P, which is stated in Newton's First Axiom as inertia. Greg Glover (talk) 15:22, 29 September 2011 (UTC)

Pound-mass is a made up unit by people who didn't know any better and then when they were asked how it was going to work with the laws of physics they thought... "oh crap we had better divide it by some arbitrary constant that we'll call gc which will just so happen to be equal to gravity and then we'll change Newton's 2nd law to F=m*a/gc so that it all works out". If you don't believe me have a look at Template:GravEngAbs. In reality if you just call a spade a spade and realize that pound is a force (with associated unit of mass being the slug), you don't need any convoluted constant or a different version of Newton's 2nd law because the normal one works just fine. 203.129.23.146 (talk) 14:54, 5 July 2013 (UTC)

In something like SI, one has eg, angular velocity (rad/s), against frequency (Hz = cycles per second), this goes all the way through as parallel systems in the same quantity. The dimensions of this is that of 1/T. One could write angle / time for angular velocity, but the angle does not appear in the torque equation, and the translation from torque to energy is via angle in radians, not cycles.

The LMFT systems are not really what they seam. In every case, one can derive F from M, without knowledge of L or T, so one supposes that F is not fundemental but derived, ie F = Mg. On the other hand, the use of measures like 'pound' (lbf) of force, like 'yard'(ie yd³) of sand or 'metre'(ie m³) of sand, is perfectly understood in contexts that are not even mentioned by the official standards people.

Of the oldest of the named SI units, most are electrical. Ten of the 17 named units come from the practical system, because in practical usage, the names do not follow the official standards but the popular ones. The provision of names like ampere vs coulomb/second, is a reality that people abbreviate names like km/h to kilometres.

What i disagree with is that quantities have dimensions: they don't. Quantities have scales, scales have units, theories connect scales, an algebra rides on the theory, and the dimensions ride on the algebra. The reason that M and F can exist side by side, is that there is an alignment of scales over g, that allows names to apply equally on both sides.

Dimensions are things you can see and measure, such as length, force, area, volume, time, electrical current, etc. so of course quantities have dimensions, otherwise they couldn't be experienced or measured. Dimensions have units and units have scales. A millimeter is a unit of length for example. Scales of different dimensional units can be overlapped (such as mm and inches). Whilst you can convert between units of the same dimension knowing only unit scales, with some additional assistance of the laws of physics you can also convert between units of different dimensions, such as mass and force (if acceleration is known). If you mistakenly treat a weight in pounds (measured on a device calibrated with pounds correctly interpreted as a force) as a mass, you will be essentially squaring acceleration under gravity when you substitute into Newton's 2nd law. 203.129.23.146 (talk) 01:05, 4 January 2014 (UTC)

--Wendy.krieger (talk) 11:12, 30 September 2011 (UTC)

Confusing "Conversion to other units" table

This table could perform a valuable service in helping readers gain traction on how these various units relate. Instead, I found it tremendously confusing because the cells on the col=row diagonal, don't make sense.

According to the row and column headers, these cells should all be occupied by the number '1'. Instead, they are occupied by a specification of the row quantity in terms of mass units (and not according to the force units in the column headers).

That information could indeed be quite useful, but I urge that it be placed in a separate column "Relationship to mass units" or some such. If it is added, please spell out the values of gn so that the relationship is clear.

Of particular significance for this article: 1 lbF, which is here shown as gn * (1 lb) (with only the link to tell us that this is lbM) should also be spelled out as: 32.174 lbM-ft/s^2. Similarly 1 kp = gn 1 kg should be spelled out as 9.8.. kg m/s^2

Hope that this achieves some consensus and can be implemented. Gwideman (talk) 03:05, 9 July 2014 (UTC)

Springing into the conversation

Traditionally, a pound force was used in engineering, other than in strength of materials or in dynamics, but as per Hooke's Law (F = kx) -- the strength of a spring was listed in the catalog specifications as force per length (expanded or compressed). This is why the official re-definition of pound as limited to a unit of mass for trade purposes is lacking. A spring catalog is of course used for trade. 173.162.253.101 (talk) 20:35, 11 May 2016 (UTC)

context

It seems that, often enough, one is supposed to know from context which unit, pound(mass) or pound(force) is meant. Jet engine thrust is commonly in pounds, and obviously enough, not pounds(mass). At a nearby air museum, a jet engine thrust is given in pounds, and converted to kg (oops). They are supposed to be fixing the sign, as there is official (Smithsonian) documentation requesting pounds and newtons. For quantities of matter, pound normally means pound(mass). Gah4 (talk) 11:45, 9 February 2019 (UTC)

They could correct it easily by changing "kg" to "kp," or to "kgf." Or, if newtons desired, "kg" to "daN" with only a 2% numerical error. 2601:14F:4500:46A0:223:7DFF:FEC4:2D73 (talk) 13:15, 29 January 2020 (UTC)

It seems that there are Smithsonian standards for museum signs that specify pounds and newtons. The one I talked to at the museum mentioned something about propeller planes that I didn't understand until I looked at one. It seems that they are rated in HP and kW, so power units instead of force units. Gah4 (talk) 14:57, 29 January 2020 (UTC)

Pounds of thrust

When I read about a rocket, for example Space X's proposed Raptor, producing "380,000 pounds of thrust", Is a "pound of thrust" the same as a pound (force)?

Either way, why is pound of thrust a red link? --John Maynard Friedman (talk) 08:20, 1 August 2019 (UTC)

A pound of thrust is a colloquial synonym of a pound-force. It could re-direct to this page, which could be improved by mentioning this synonym. Dondervogel 2 (talk) 08:45, 1 August 2019 (UTC)

 Done --John Maynard Friedman (talk) 12:57, 1 August 2019 (UTC)

Yes, I agree. See the section above. It doesn't make sense for jet or rocket engine thrust to be specified in either pounds(mass) or kilograms. Gah4 (talk) 23:35, 24 November 2019 (UTC)

More on unqualified "pound"

The first paragraph of the article is problematic. In actual practice, the term "pound" and the abbreviation "lb" are used both for "pound mass (lbm)" and "pound force (lbf)." Both are correct. Where the meaning of "lb" isn't clear from context and the habits of the particular technical community, using "lbm" or "lbf" is not a bad idea. What is incorrect is the suggestion that the unqualified unit "pound (lb)" specifically means "lb mass" and not even to mention the qualified abbreviation, "lbm." In the past some authority may have defined it that way but in fact both conventions are popular. 2601:14F:4500:46A0:223:7DFF:FEC4:2D73 (talk) 04:27, 22 January 2020 (UTC)

Article needs a full cleanup to not be based from SI units

The conversions can live in their own entry at the end. The article is about pound-force, from the foot-pound-second system. There are many other articles that need this cleanup too. 38.92.150.242 (talk) 06:21, 27 March 2024 (UTC)

Thank you for your suggestion. I reverted your edit because it introduced an error in the value of standard gravity, which is defined in SI units (9.80665 m/s). Please make or propose changes incrementally so each one can be assessed on its merits. Dondervogel 2 (talk) 07:21, 27 March 2024 (UTC)