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Pound mass/weight

I don't want to comment on the debate about whether a pound is mass or weight, because both meanings are used in different contexts.

This comment takes issue with the statement, re conflating mass and weight: "resulting from the near uniformity of gravity on Earth." No, the conflating of mass and weight has nothing to do with that. Before modern technology, serious weighing was not done with unreliable spring devices, but with a balance scale. A balance gives the same result regardless of field strength. A one pound reference object will balance one pound of butter exactly, whether it is on the Earth or on the Moon.

I think people are confusing two different dichotomies. The first is the basic difference between the distinct physical concepts of mass and weight. (The weight refers to the force of gravity on the mass.) There is a separate issue of distinguishing between inertial mass (which is best measured directly by accelerating it at a specified rate and measuring the force, F, required to do this, then calculating the mass using m = F/a), versus gravitational mass, which is directly measured by measuring the force required to suspend the object, then dividing by g, the observed acceleration of an object falling due to gravity, i.e. m = F/g). It turns out that both methods of measurement produce identical results.

So, the weight (the force of gravity on the object) is directly proportional to the object's mass, and therefore finding the weight also determines the mass (which is obtained simply by multiplying by a constant and changing the unit). On a balance scale, if the weight of an object is balanced by the weight of a reference object, then the two masses must also be equal. This has nothing to do with the strength of the gravitational field, which is why I am suggesting the removal of the inappropriate phrase, "...resulting from the near uniformity of gravity on Earth." 77Mike77 (talk) 03:11, 3 February 2013 (UTC)

I don't claim that paragraph is especially well written, but it does go on to say "this accounts for the modern distinguishing terms pound-mass and pound-force." So I think the paragraph refers to the experience of people who lived at the time the word "pound" was adopted, that an object with a mass of one pound required a force of one pound to lift it, unless it was under water. Those people had no access to places where it would take substantially more or less force to lift the one pound mass (in air), so it didn't occur to them to invent one word for a unit of mass and a different word for a unit of force. Jc3s5h (talk) 04:27, 3 February 2013 (UTC)
Firstly, it is inappriopriate that this is mentioned in the lede, but not in the body of the article. From a UK perspective, I don't think it appropriate to mention this in the lede, but it certasinly has a place in the body of the article - nobody in the UK uses pounds in areas where this is of consequence. Americans might think otherwise - I am open to comment.
Secondly, it was only in 1901 that the CGPM differentiated between the use of the word "mass" and the word "weight". I know that UK law, when refering to the pound uses the terminology "mass or weight". At the present time, the kilogram is defined in terms of a piece of metal and the pound avoirduois is defined in terms of the kilogram.
Thirdly, air, like water, provides bouyancy - it has a density of 0.12% that of water.
Martinvl (talk) 09:41, 3 February 2013 (UTC)
Pound is used as a unit of force, mostly as part of a compound unit, in important ways in the US. Pressure is often measured in pounds per square inch (PSI). Torque is often measured in foot-pounds.
Also, focusing on legal definitions may give only a partial picture, because the law tends to focus on commerce, especially things that weights and measures officials inspect. Since weights and measures officials make many inspections of mass measuring devices, but seldom inspect pressure gauges or torque wrenches, focusing only on legal definitions may give a biased view. Jc3s5h (talk) 02:42, 4 February 2013 (UTC)

The word "weight" comes from the verb "to weigh", which has a connotation of balancing. We talk of "weighing the possibilities", or a judge "weighing the evidence" before reaching a decision. The "weight" was a number obtained from balancing the unknown mass with a tray of known masses. The word "pound" comes from the same root as "ponder", and the symbol "lb." is short for libra, meaning scales. The merchants who used these scales weren't physicists, and did not have calibrated springs from which masses could be dangled to find the force of gravity by measuring the stretch distance. The "weight" was simply a number obtained by balancing the unknown on a scale. This predated the theory of gravity. This is all utterly simple with the metric system, where mass is kilograms and force is newtons; the confusion arose in trying to re-invent the British system to make the distinction between mass versus the force of gravity on the mass (i.e. the weight of the mass).

Reading the discussion is like watching people enmired in quicksand. There is nothing complicated about this. The concept of a pound was not invented by people contemplating the pull if gravity. To be consistent with physics, a pound is a unit of force, but in common usage it also refers to the mass that is attracted to the earth with a gravitational force of one pound. The question of tiny variations in gravitational field strength, as well as the extremely slight buoyancy of the atmosphere, are of no practical importance in common usage, and a physicist who is studying those details would be using metric units in the first place.

The phrase "resulting from the near uniformity of gravity on Earth" is categorically false, and discredits the entire article, and it is necessary to remove that phrase before spending time trying to improve the rest of the article. Overall, the article is very good, but that one phrase would make any physicist spit up his coffee. 77Mike77 (talk) 02:27, 4 February 2013 (UTC)

Is there some reason you have not made the edit already? Either go ahead and make it or else post some proposed text on this page. It is much easier to get focused comments once we have some actual words. SpinningSpark 12:38, 4 February 2013 (UTC)
One correction: In physics the pound is a unit of mass, not force. It is engineering where the pound is a unit of force. Hans Adler 13:41, 4 February 2013 (UTC)
Hans Adler can't back up such a definitive statement. Scientists and physicists work mostly on a basis of consensus rather than laws and regulations, so the answer would depend on which group of engineers and physicists you ask. And you'll never be able to draw a bright clear boundary between physics and engineering. Jc3s5h (talk) 13:57, 4 February 2013 (UTC)
Rather than entering into an argument as to whether the pound is a unit of mass or of force, is it not better to dicsuss what this article will cover and how it will be covered? This article's name is "Pound mass" and there is an article Pound (force). Martinvl (talk) 14:16, 4 February 2013 (UTC)
I am aware of that. My statement was intended as a vague one on trends in the two communities. It was prompted by the opposite statement, which was either precise and completely wrong or similarly vague and mostly wrong. Hans Adler 14:20, 4 February 2013 (UTC)

Hans, what you wrote is absolutely false. For example, a foot-pound is a unit of work (energy), which makes no sense unless the pound is a unit of force. It may be that there are places in the UK where physics students are allowed to assume that an unqualified pound refers to mass, but this is certainly not the case in North America. Common usage is, of course, also inconsistent. A pound of butter refers to mass. Tire pressue (pounds per square inch) refers to force per unit area. Simply assering something with conviction does not make it so.

Spinning: yes, there is a reason I didn't make the edit yet; namely, every multi-word edit I've made on WP has been reverted, with accusations of vandalism. But thanks, I'll simply delete the offending phrase.77Mike77 (talk) 15:03, 4 February 2013 (UTC)

When you're near the surface of the earth -- as most of civilization has been for most of its existence -- gravity is a constant and thus there is no practical difference / significance between mass and weight. It was only when Newton articulated the fact the force dropping apples and the force making planets go in ellipses was the same thing that the distinction between the two of them made any difference. Even today, in most areas of human activity, the distinction isn't made. When you purchase food by weight at the grocer, you don't pull out a pendulum to verify the force of gravity hasn't changed since the scale was calibrated (I hope). If gravity was 9.80 m/s2 in Athens and 7.00 in m/s2 in Sparta the ancients' model of the world would have been quite different.
Meaning depends on context and scientists and engineers are expected to know what they mean. For example, foot-pound may be a unit of energy -- but it isn't if it's actually a torque. NE Ent 16:54, 4 February 2013 (UTC)
Maybe we can agree that usage in the physics community is divided even in the US. [1]
You seem primarily concerned about the US, but already the 1911 edition of Encyclopaedia Britannica was explicit about the pound as a unit of mass in the UK in one article ("The fundamental units of these systems are -- of length, the yard and metre; and of mass, the pound and kilogram." [2]) and as a unit of weight in another ("POUND (2) - (a) a measure of weight;" [3]), which it defines elsewhere as a force ("The term 'weight' denotes a magnitude of the same nature as a force;" [4]). Hans Adler 18:13, 4 February 2013 (UTC)

The ancients didn't use spring-loaded scales for weighing, they used balance scales, and so the non-uniformity of the gravitational field is irrelevant. A pound of butter will exactly balance a reference pound of lead, whether on Earth, the Moon, or an asteroid; this was not a factor, and it was incorrect to claim that it was. The claim was likely a personal guess, based on confusion, and there was no citation to back it up (nor will one be found). "Weighing" meant "balancing on a scale", and the "weight" was a number they obtained by this process. The distinction between "mass of an object" and "gravitational force on an object" had not been invented yet, so the ancients were not overlooking anything by using the term "weight" in a way that ignores later refinements in physics.

We don't seem to be in disagreement about the fact that the UK and North America have different conventions about the use of the word "pound". This seems to be a grammatical difference, like the different meanings attached to the word "lumber". I don't think we can say, on the world wide web, that one defintion is the "real" definition. Here in Canada, we have an informal kilogram-force, which is what a spring scale measures, but that is a whole other can of worms. Physicists don't use these informal terms, and generally do not use avoirdupois units at all when doing physics, So the article should be focused on the usage outside of physics. In Germany, there is a commercially used "metric pound" (500 grams). And how does one weigh a helium-filled balloon? It doesn't matter, because nobody buys them by the pound. Thank you for your informative comments.77Mike77 (talk) 20:21, 5 February 2013 (UTC)

The scale only balances equal masses because the gravitational field is uniform. If the gravitational field was stronger at one pan than the other unequal masses would actually "balance." The word "pound" in North America means many things, as Wikitionary outlines well. NE Ent 03:21, 6 February 2013 (UTC)
While technically true, failure of local homogeneity would be very unusual on any body, and I think that at most a small minority of readers would have understood the sentence in this sense. Hans Adler 07:37, 6 February 2013 (UTC)

Pound riddle.

I removed the volume comparison section because the discussion relating to feathers is somewhat nebulous - just how compressed are the feathers when checking their volume? Also, where did you get the density of the feathers - air has a density of 0.0012 g/cc, so is 0.0025 realistic? Martinvl (talk) 20:12, 19 June 2013 (UTC)

I got it from [5] which references [6]. I don't know how they derived it; perhaps they just doubled the density of air? It's a fair comment that the feathers would compress due to self-weight, but 182 litres isn't really that much (especially if spread out, and not, say, in a tall column). Nevertheless, I think it does give a better visualisation of the quantities involved. cmɢʟee୯ ͡° ̮د ͡° ੭ 12:02, 24 June 2013 (UTC)
I am still not happy with the density of feathers - has Archimedes' principle been taken into account in respect of the buoyancy supplied by air. How much have you taken into account "surface air" on the feathers - air which occupies the spaces between the feathers? Finally, the troy pound ceased to be legal in the United Kingdom in 1878, though the troy ounce is still legal for precious metals. Martinvl (talk) 14:10, 24 June 2013 (UTC)
I didn't measure the density myself (if I did, it would be considered Original Research anyway); I'm just citing the published source. Based on the example use of the table in the article, buoyancy seems to have been accounted for, so it's what the feathers would weigh in air. It's useful to know, though perhaps irrelevant whether it's legal or not in the context of the riddle. cmɢʟee୯ ͡° ̮د ͡° ੭ 17:58, 26 June 2013 (UTC)

Pound of feathers vs pound of gold riddle

User:Blue-Haired Lawyer wrote in edit summary "I think (w)e can all agree riddles are unencyclopedic." Well no, posing riddles might be unencyclopaedic but providing answers to them certainly isn't. The criterion for inclusion is whether the riddle is discussed in reliable sources.

Like user:Jc3s5h I am neutral on whether we want this in the article, but I think it should be discussed here first before any more insertion/removals in the article. SpinningSpark 14:46, 23 August 2013 (UTC)

The content was;

==Pound of feathers vs pound of gold riddle==
The riddle, "What weighs more, a pound of feathers or a pound of gold?" assumes the use of different pound units to measure the two substances — avoirdupois for feathers and Troy for gold. As an avoirdupois pound (approximately 454 g) is heavier than a Troy pound (approximately 373 g), the correct answer is, "A pound of feathers." [1][2]

References

  1. ^ Eureka! American Museum of Natural History
  2. ^ Demos — Making Science Fun! Yale University

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Dutch pound

Is there a source for the claim that the modern Dutch pound is a kilogram rather than half a kilogram? I disbelieve the current assertion. The article titled Dutch units of measurement says it's half a kilogram. Michael Hardy (talk) 18:14, 5 May 2014 (UTC)

There are plenty of sources for just the opposite [7][8][9][10][11][12] SpinningSpark 20:18, 5 May 2014 (UTC)
Perhaps the confusion comes from 10 ons = 1.0 kg SpinningSpark 20:23, 5 May 2014 (UTC)
In modern usage the Dutch 'pond' is equal to 500 g. Dondervogel 2 (talk) 19:34, 22 May 2017 (UTC)

Ounces and pounds of mass

On the ounce article, one or more anons (several different IPs, but they seem to act as the same person) is insisting on defining an ounce as a unit of weight (force) rather than mass. Since the customary units are defined in terms of the metric units of mass, they too must be units of mass. Could others please contribute? Thanks, --Macrakis (talk) 03:35, 9 November 2017 (UTC)

I understand your confusion, however the existing statements that ounces and pounds are weights is accurate, and should remain. In Imperial and U.S. Customary unit systems, the pound (and thus ounce) were defined before the difference between weight and mass was clearly understood, and are thus measurements of weight, even though additional engineering units for force were later grafted onto the system(s). Among measurement systems that Americans an British are familiar with, only the metric/SI system clearly defines these separately. So while the value of the International Pound (and ounce) is defined by the SI unit for mass, that does not make the ounce a unit of mass after the fact of its original definition (I view the metric definition of the pound as a refinement/official conversion, not as the original definition, which is of course 7000 grains. But that's another article. (And I might add that your question is a good one, which exposes the problems of continuing to use customary units. Metric is sooooo much simpler. PetesGuide (talk) (K6WEB) 04:58, 10 November 2017 (UTC)
If you had an ounce of gold in your pocket, would you still have an ounce of gold if you climbed to the top of a mountain? How about if you took an international flight or visited the international space station? Does the amount of gold in your pocket change as you move between these different places? By the way, WP:SIG#EL says a signature should not have an external link. Johnuniq (talk) 06:42, 10 November 2017 (UTC)
I feel that PetesGuide has it semi-right. The question is not whether 'ounce' is a unit of mass or a unit of force; it is obviously a unit of mass, in the context of scientific discussion. The question really is: What is the English word for mass in the context of an ordinary ("non-scientific") discussion? I last lived in England in the 1980s, so I can be accused of being out of date, but the answer until then was quite clearly "weight". In a "Guess the weight of the cake" competition, or when it says "Weight 8 oz" on a bag of sugar, these clearly refer to the amount (mass) of cake or sugar present. The usage is justified by the "historical conflation of mass and weight", which is in turn justified in non-precision contexts by the fact that gravity is a constant. (In modern Britain, for example, does anyone really say "Give your height and mass"??) This conflation is also justified in practice by terms like "Kitchen scales" which conflate the nonexistent terms "massometer" (a balance) and "weightometer" (a spring or piezoelectric force measuring device). I do not see that the metric system makes any difference at all. The ordinary word for "how much stuff there is" is "weight", as in "my weight in kilos", in contrast with "how much space the stuff takes up", which is volume. Imaginatorium (talk) 07:26, 10 November 2017 (UTC)

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What about lbs?

Maybe add info also for the lbs? And differences between pound/lb/lbs (if there are any [for people who doesn't use imperial/United States customary systems of measurement])?

Difference between Lbs and Pounds

Why are pounds, when used as a weight, abbreviated lbs? --89.25.210.104 (talk) 19:09, 17 May 2018 (UTC)

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