Talk:Weight/Archive 1

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This page is basically a long argument that the historically correct usage of weight is mass. But the origins of words do not determine their proper use, and anyways, weight was first coined back when people didn't have any concept of the distinction between mass and force due to gravity. I've removed the bit about scales, since it is the least sensical - scales measure force due to gravity in circumstances where it will ideally be proportional to mass, so to claim they are truly measures of one or the other seems kind of absurd. The rest could stand some editing, though. The distinction between pounds and pound-forces is not supported by older physics texts, which usually use pounds as forces and slugs for mass, while acknowledging a different system where pounds are masses and poundals are forces.


Admitedly the terminology for pounds is confusing, but you will find that the legal definition of pounds in the United States today is as a unit of mass.

A balance scale compares masses, it does not measure force due to gravity. You put the object to be weighed on one end of the balance. You then add weights of known mass on the other end of the balance, until the balance is level. This procedure requires acceleration due to gravity to work, but doesn't depend on the actual value of the acceleration. So it is a measure of mass, not force due to gravity. -- SJK

Disagree. You can use the exact same device to measure charges in an electromagnetic field, or the relative strengths of two springs. It's only measuring mass when you decide to interpret the results as mass; when you decide to interpret them as forces, it's measuring forces. It doesn't make any sense to talk about what a device is "truly" measuring when it's measuring two coincident things! I really think this article's emphasis on whether or not usages are correct, rather than what weight is, is a bad thing, and would vote for this passage to be removed and others to be rewritten, but I don't want to get into a back and forth edit war.

But when you use it to compare masses, the result does not depend on the force due to gravity. A scale balance will give you the same result on Earth as it will on Mars. A spring balance will not. -- SJK

However, scales depend on factors other than the masses and force due to gravity. When you try to use scales underwater, and the objects being weighed do not have the same density, you get incorrect measurements. Actually, this phenomenon (Archimedes' Force) occurs in any medium other than a vacuum, but it is almost negligible in air. In general, if you apply some vertical force on the masses, you mess up the scales' readings. What they really do is compare the forces acting on each side of the balance. Thus, I would not say that they measure mass. For something to measure a quantity, its output has to depend only on that quantity. For example, a barometer always measures air pressure; although it can be used to calculate elevation (if you know the relationship between elevation and air pressure) that is not what it actually measures. --KA


Minor correction: scales do not measure forces. If they did, the doctor's office couldn't weigh you with those small masses on the scales. Scales compare torques: when torques are imbalanced, the lever arm rotates, when the lever arm holds still the torques are the same (in opposite direction). Add a little geometry, and you can convert the torques to the net force directed radially. That is as much as you can say about a balance without adding other factors. If the forces are applied to the ends of strings attached to the lever arms of the balance (much the same way many balances have susbended trays on them) you can tell the direction of the force (a useful way to convert radial force to net force). To get to a measurement of mass takes: 1, a unidrectional field (maybe, this one could be corrected for with the strings, I'd have to think more to say for sure); 2, a uniform field (at least uniform enough that the geometry of the balance and/or the object does not effect the net force); 3, a field that is only proportional to the quantity you wish to measure.

BlackGriffen


Maybe this page explains what I was trying to get across better http://ourworld.compuserve.com/homepages/Gene_Nygaard/weight.htm

The comments still apply. Ancient peoples couldn't be talking about mass as opposed to gravitational force if they didn't have distinct concepts of each. Scales measure mass when you use masses for reference and forces when you use forces for references, and so to speak of them truly measuring one or the other is silly, modulo KA's comments above. And, btw, does anyone know if there is an official usage for the pound in Britain or elsewhere? America hardly determines universal standards for units, as the gallon proves.


The pound (technically, the pound advoirpois) is defined in the same way in both countries, since the 1950s, in terms of the kilogram. -- SJK

Ok. Well, one still finds a considerable body of literature using pounds exclusively as a unit of force, especially in derivative units (e.g. 550 foot-pounds/second = 1 horsepower), and it would be somewhat hypocritical to talk about historical usage and then turn around and label these as simple obsoletes. I think that, when usage is varied, an article should reflect varied usage and not try and impose a false order on reality.

An example of a case where common usage refers to force, and not mass, is when people say objects in space are weightless.


I'm not saying that weight cannot mean force, just that it is historically mistaken to claim that it should only mean force, or that people who say that "I weigh 50kg" are somehow being inaccurate.

Also, yes people in past centuries weren't entirely clear on the difference between mass and force due to gravity, but most of the time it was mass, not force due to gravity they were worrying about. If you weigh out 5 troy ounces of gold, do you want 5 ounces mass or 5 ounces force due to gravity? You are interested in the mass, not the force due to gravity. Similarly, if an apothecary weighed out 1 grain of some medicinal substance, they wanted 1 grain mass, not 1 grain force. Weighing is (and more importantly was) most commonly done to determine the amount of substance, not to determine how heavy it is. So even if they weren't entirely clear on the difference, they wanted mass. -- SJK

On Earth, weight refers to that quantity which is both mass and gravitational force because the two are identical there, and elsewhere the meaning is considerably clear. It doesn't matter which of mass and force people really wanted to be talking about back when they didn't distinguish the two, because they didn't distinguish the two. Nowadays the word tends to mean force when there is a difference, though it still is used to mean mass a lot of the time. Language changes. We want to reflect use, not what we believe use should be, or what we believe historical use better represented - actual historical use being of course both simultaneously.

The bit about scales I'd like to see removed, since as argued above it is incorrect, and the bit about weight historically meaning mass I'd like to see altered, since it is misleading at best. I'd also like to see the approach to legal resolutions straightened out, since we seem to accept the universality of the recommendation that pounds be mass but treat the recommendation that weight be force as a mere suggestion. If I change the article to take these into account, can I trust that you will not revert it, at least not without further discussion?


How about:

Weight, in physics the force that gravity exerts on a body. Compare mass.

What's all the fuss about? Sheesh. Ed Poor


At the very least, we should make clear that, historical usage aside, this encyclopedia uses the term weight to refer to force due to gravity. Otherwise, every link to this article will leave the reader confused: "Which meaning of weight are they currently using?" --AxelBoldt


I've finally done it, I've gone and blown it all up. Right now the article says that weight should mean force, at least in technical literature, which is possibly overkill but already present in the new introduction, and certainly in line with both what seems to be wikipedian consensus and the CPGM resolution. The stuff about weight historically meaning one or the other has been removed, since they were not distinguished and it is a bad idea to try and determine which people really meant, and the stuff about scales actually measuring one or the other has been removed, as the above comments (not all by me) provide ample justification for such a change, I'd say. I apologize for how radical this edit is and how completely it reverses the position, and would be more than happy for SJK or someone else to temper the article somewhat towards accepting mass as a valid alternate. I just don't think we should try and argue that it is somehow a better meaning.

(This means that most of this Talk page is now obsolete...)


Oops, I did it again (with apologies to B. Spears) I missed the SI thing at the bottom. So, let's discuss how to make the article serve all its purposes

  • distinguish between weight and mass, so we know which is which.
  • point out that they're still used interchangeably (at least by laymen)
  • give some sort of endorsement to the scientific usage.
I think the current article does just that, no? --AxelBoldt

When discussing scientific or engineering matters, I take pains to use force (measured in N-m or lb-ft) to mean force. But contemporary usage is fraught with references to 'weight' which "really" refer to mass. I used 'weights' on a balance scale to 'weigh' objects and determine their 'weight' (really mass, of course) in high school science classes.

N-m is work or energy, not force. --AxelBoldt

How weighty an issue is this, anyway (wink)?

Ed Poor

Too much jargon

Some people seem to have lost sight of the fact that this is an encyclopedic article, not merely a guide ot the interpretation of the jargon of particular petty priesthoods.

This is also a word is quite general use, and with quite specific meanings—meanings often at variance with the jargon of those priesthoods.

We would better serve our readers by making these distinctions clear. Enough of this burying your heads in the sand. Gene Nygaard 14:46, 17 Dec 2004 (UTC)

Scope of this article

In determining what should be included in this particular article "Weight" it is instructive to look at how the word is used on the pages on the "What links here" special page.

However, keep in mind that most of these are nothing more than brief mentions, not using any actual measurements of anything called weight.

Some might quibble with my characterization of almost every individual linking article, but if you want to comment on that it would be more helpful to discuss a broader class of them by the context in which "weight" is used in that group of articles.

Omitted are a redirect from Falling and five double-redirects under it.

I stubbed a new falling that includes a basic classical physics definition and some other lovely descent-related stuff. --Tony Sidaway|Talk 22:30, 2 Jan 2005 (UTC)

What links here? sorted by meaning

means mass Balance
Clinical depression
Fetus
History of computing hardware
Sputnik 1
Tupolev Tu-144
W. G. Grace
Stone
Physical collision
Clozapine
Weight training
Sinker (fishing)
Universal Product Code
Valproic acid
Commercial at
Tael
Tandem bicycle
Jam
Power-to-weight ratio
Haloperidol
Fluphenazine
Typical antipsychotic
Risperidone
Crash test dummy
Rechargeable battery
14 (number)
Canon de 65 M(montagne) modele 1906
Canon de 75 M(montagne) modele 1928
Unsprung weight
Oka (measure)
Cephalic disorder
Local food
Avoirdupois
Tonnage
Talk:Grain
Self image
Obolus
Wikipedia talk:WikiProject Space missions
Dick Tiger
BattleTech:Technology
Comptometer
talk:W. G. Grace/temp
oka (measure)
ThinkPad X40
CWT
Hundredweight
Little Britain
Ra's al Ghul
Blood donation
Trevalla
Rolled Homogeneous Armour
Terex Titan
LCM-8
Units of measurement
Aston Martin DB7
Devaluation
Tower pound
British 81 mm mortar
Thrust-to-weight ratio -- also used for an imaginary force
Code Adam
Displacement (fluid)
RCMP recruiting
User:Patrick/w
Haugh unit

means force due to gravity Aeronautics
Aerodynamics
Centripetal force
Fall
Hail
Mass
Oscillation
SI derived unit
Weightlessness
Relative density
Gravitational constant
Specific impulse
Gee
Talk:Newton (disambiguation)
Newton
Talk:Newton (unit)
Freefall
Connection
Pound-force
Terminal velocity
Thermostat
Structural analysis
Unit of account
Soap bubble
List of topics (scientific method)
Boussinesq approximation
NLGI Grade
Image:Aeroforces.jpg
Allen Carr
Talk:Relative density
Wheelbase
Diplexer
User talk:GK
Normal force
Apparent weight -- but a variant meaning of word without adjective
Gravimetry
Animal locomotion
Animal locomotion on the surface layer
Decompression trapeze

means density Bone
Apheresis

means an object Gravity
Weight training
Timeline of gravitational physics and relativity
History of perpetual motion machines
Diving shot
Spotter
Hydraulic accumulator
William Congreve (inventor)
Tsukemono

means both mass and force due to gravity, may be different people, esp. in talk Pound
Scientific method
Amedeo Avogadro
Talk:Mars Exploration Rover Mission
User talk:80.255/archive 1
Wikipedia:Reference desk archive/June 2004
Talk:Internet
Weighing scale

could mean either mass or force due to gravity, or meaning unclear Aircraft
Mineral
Metallurgy
Talk:Sputnik 1
Buoyancy
Bulldozer
Weight bearing
Bar (unit)
Naruto geography
Hip dysplasia
Outrigger
Powered armor
Talk:Crash test dummy
Monosoupape engine
Tamp
Burden

means force, but not due to gravity, or not just gravity Action stroke dance notation
Thrust-to-weight ratio -- also used meaning mass

mathematics jargon meaning Weight function

do not use weight (other than link to here) Scale (measurement)
Fundamental unit
Heavy
Human physical appearance
List of physics topics R-Z
Cranial electrotherapy stimulation
Magic School Bus episode guide
List of -ight words
Wikipedia:Concise
User:Anthony DiPierro/Everything else

means none of the above Deadbolt


What links here? Sorted by units used for "weight"

This is the most instructive part—looking at how the word "weight" is used when it us used with actual measurements.

Note also that there are hundreds of other pages on Wikipedia which do measure other quantities identified by weight, but which do not link to this page. I'd bet that they are even more unbalanced towards the measurements of mass than this listing.

mass, uses kg, lb Pound
Sputnik 1 -- uses kg, lb
Tupolev Tu-144 -- uses kg only
W. G. Grace -- uses kg, stone (no lb)
Weight training -- uses lb, kg
Sinker -- uses oz, lb
Commercial at -- defines at, arroba in terms of lb
Tael -- defines tael using oz troy and avdp, g
Crash test dummy -- uses kg, lbs
Canon de 65 M(montagne) modele 1906 -- uses kg only
Canon de 75 M(montagne) modele 1928 -- uses kg only
Oka (measure) -- just defines oka in kg
Avoirdupois -- just defines lb in grams, other units in lb
Tonnage -- just defines various tons in terms of kg or lb
Obolus -- just defines in terms of grams
Dick Tiger -- uses "pds"
BattleTech:Technology -- uses tons
talk:W. G. Grace/temp -- uses stone only
oka (measure) -- just defines in kg
ThinkPad X40 -- uses kg, lb
CWT -- just defines in lb
Hundredweight -- defines in kg, lb
Little Britain -- uses stone
Ra's al Ghul -- uses kg, lb
Diving shot -- uses kg, lb
Trevalla -- uses kg only
Terex Titan -- uses tonnes only
LCM-8 -- uses tons (probably long tons) only
Units of measurement -- just defines lb in kg, kg in "weight" of liter
Aston Martin DB7 -- uses tonnes only
Tower pound -- just defines in grains
British 81 mm mortar -- uses kg only
Code Adam -- uses lb, kg
Tsukemono -- uses kg only
Displacement (fluid) -- uses long tons
RCMP recruiting -- uses kg, lb
User:Patrick/w -- uses kg
Ruby Lin -- uses kg, lb
14 (number) -- just definition of stone in lb

force, uses newtons, kgf, lbf Specific impulse --uses N, and sort-of uses gf
Newton -- just defines, doesn't use, N
Talk:Newton (unit) -- just N, kgf definition
Normal force -- uses N
Animal locomotion on the surface layer -- uses dynes only

use no units for "weight" I'll leave these jumbled together and unlinked.
Aircraft Aeronautics Aerodynamics Bone Balance Centripetal force Clinical depression Fetus Fall Gravity History of computing hardware Hail Mass Mineral Metallurgy Oscillation Scientific method SI derived unit Weightlessness Relative density Stone Gravitational constant Collision Amedeo Avogadro Clozapine Scale (measurement) Universal Product Code Valproic acid Gee Fundamental unit Timeline of gravitational physics and relativity Talk:Newton (disambiguation) Freefall Tandem bicycle Talk:Sputnik 1 Jam Power-to-weight ratio Connection Pound-force Heavy Haloperidol Fluphenazine Typical antipsychotic Risperidone Rechargeable battery Human physical appearance Unsprung weight Cephalic disorder Local food Buoyancy Talk:Mars Exploration Rover Mission Terminal velocity Thermostat Structural analysis Talk:Grain Unit of account Bulldozer Weight bearing Self image Wikipedia talk:WikiProject Space missions Bar (unit) Soap bubble Naruto geography User talk:80.255/archive 1 List of topics (scientific method) Boussinesq approximation List of physics topics R-Z Comptometer Hip dysplasia History of perpetual motion machines Cranial electrotherapy stimulation Magic School Bus episode guide Outrigger Blood donation Spotter Rolled Homogeneous Armour Devaluation Powered armor Talk:Crash test dummy Hydraulic accumulator Action stroke dance notation William Congreve (inventor) Monosoupape engine Deadbolt Wikipedia:Reference desk archive/June 2004 NLGI Grade List of -ight words Image:Aeroforces.jpg Allen Carr Talk:Relative density Wheelbase Talk:Internet Diplexer Weighing scale Apheresis User talk:GK Apparent weight Gravimetry Animal locomotion Tamp Wikipedia:Concise Decompression trapeze User:Anthony DiPierro/Everything else Haugh unit Burden

restoration

Body wt is a common (perhaps the most common) use of the word and predates the largely theoretical distinction between wt and mass. 99+% of our readers don't know the difference and should be at least educated, oriented, and sent to their topic of interest. I hope it doesn't pain you too much to retain the two small sections at the end even though I applaud your efforts at scientific rigor. alteripse 02:46, 5 Feb 2005 (UTC)

Latest edits by CYD

I'm glad to see that you are finally coming to your senses about this, CYD. Your last edit is much more reasonable than what you reverted to earlier. With a little more tweaking, it might even work.

However, your comment about "remove self-promotion link" is misplaced. That was here before I ever started editing Wikipedia (my first edit of any kind was 6 Dec 2004). You can see where it is mentioned in an unsigned comment here on this talk page; if you look in the history, you can see that it, and the link on the article page, were added more than three years earler, see talk page Revision as of 22:47, 2 Dec 2001 203.109.250.xxx . Though I wouldn't know how to do it myself, I have no doubt that somebody could track down that user as being someone other than me. Or maybe I did; some edits by 203.109.250.xxx are signed [[SJK]] and entries signed by SJK also appear on this talk page, and the comment about adding the link is worded as an extension of some of those comments.

Nonetheless, I don't think it would be appropriate for me to reinstate your deletion of the External link to my web page, though I have no objection if someone else choses to do so. Gene Nygaard 03:46, 5 Feb 2005 (UTC)

Who is more careful?

The statement that "In the physical sciences, people are usually more careful about the distinction between weight and mass" is a crock of nonsense.

First, it assumes facts not in evidence—that there is in fact always a "distinction between weight and mass". It is a logically flawed, circular argument to assume this as a fact in the first place, and then use it to prove the same point.

Second, the usage of the word "weight" is much more consistent and uniform in commerce than the usage of the word "weight" in the physical sciences.

  • Commerce usage:
    • Weight is never a force when anybody talks about net weight of anything.
    • You never hear of any government regulator mistakenly testing a scale used in commerce for its accuracy in measuring force rather than its accuracy in measuring mass. But then, they have a lot of shoulders to stand on; this was already old hat when Hammurabi included provisions regulating this weight in his Code of Laws some 3750 years ago.
    • The troy units of weight, which are still used in commerce (even in the 21st century enjoying a special exception from the metrication laws of places such as Australia and the U.K., are always units of mass, never units of force. Those troy units were also the preferred units of Isaac Newton in the physical sciences (perhaps because he could borrow the scales of his employer at his day job as Master of the Mint), even though he liked the French toises, pieds, and pouces for length.
    • Weight is never a force when anybody talks about carcass weight, even if they spell it carcase weight.
    • Weight is never a force at the livestock auction markets in Saskatchewan, whether they are selling hogs in dollars per hundred kilograms or cattle in dollars per hundred pounds, which is no matter how you look at it a pretty weird way of doing things.
    • Newtons are never legal units for the sale of goods by weight.
  • Physical sciences usage:
    • Despite CYD's wishful thinking, the terms atomic weight, molecular weight, and formula weight are alive and thriving.
      • Just go look at a few of the zillions of Periodic Tables of Elements cluttering up the World Wide Web, and see how many of them use atomic weight (on many of them, you get details like this by clicking on the symbol for each element). Many of these are posted by educational institutions around the world.
      • Google—
            "molecular weight"                     3,250,000 hits
            "molecular weight" site:harvard.edu       12,600 hits
            "molecular weight" site:nist.gov           5,490 hits
    • The rocket scientists at NASA tell us that the weight of the Apollo 11 Lunar Module at liftoff of its ascent stage was 10,776.6 lb.
    • The thrust-to-weight ratio of that LM, in normal NASA usage of this term, was about 0.35 or less (they usually omit the units). Do the math. And the dimensional analysis.
    • The verb to weigh is considered correct when used to mean "to measure the mass of" something, even when used by those who would not use the noun weight for the result of that weighing. Using to mass as a verb with this meaning is substandard usage which grates on the ears of most people, including many chemists and physicists.
    • Physical scientists are often called on by their governments to help in the development of weapons of war. Go look into how the term throw weight is used. What are the proper SI units for this quantity? Hint: it is the same units used in various treaties.
    • Then, of course, there is Henry Cavendish's paper, Weighing the Earth, a title never to be spoken aloud in an astronomy class.
  • Deceptiveness in the "physical sciences" classification:
    • Those making this claim would like to have us believe that they are making broad generalizations about the entire scope of science and technology in general. So what we need as an aid to this discussion is the following glossary entry:
      • Physical sciences: a term referring the mechanics sections of introductory college physics textbooks published after 1980.
  • The physical sciences usage they'd like us to forget about:

Then there's that heavy cream those physical scientists use in their coffee. No matter which definition of weight we use, a liter of heavy cream will weigh less than a liter of light cream! — Gene Nygaard 11:11, 5 Feb 2005 (UTC)

I think the assertion that, in the physical sciences, "weight means a force" is mostly correct. In any case, the physical sciences do not include Engineering, biology, paleontology, medical sciences, verterinary science, agricultural sciences, archaeology, or aeronautics (in the sense of engineering). I don't know how to categorize the use of crash test dummies. --SV Resolution(Talk) 20:30, 10 November 2005 (UTC)
The "physical sciences" is a context-sensitive term, with many different variations in meaning. It often includes engineering. See, e.g., Webster's Third New International Dictionary and various versions in the history of the physical science article. It is also very often used as a distinction from "social sciences" (and, in that context, including the biological sciences).[1]
But none of that really matters in the face of 7,390,000 Google hits on the exact phrase "molecular weight", including 9,130 of them on "site:en.wikipedia.org". (I must have hit Google on a bad day in the numbers quoted above.) That doesn't even get into "mol. weight" and "mol. wt." and "atomic weight" and "at. wt." and "formula weight" and all the similar usages.
Those are usages in what would be called the "physical sciences" in any of its various definitions. Gene Nygaard 12:36, 11 November 2005 (UTC)
How about "In the physical sciences, weight generally means the interaction of matter with a gravitational field"? --SV Resolution(Talk) 21:00, 11 November 2005 (UTC)


For discussion of the atomic weight, here are the google hits:
Atomic weight: 3.130.000
Atomic mass: 25.300.000
Must you have searched on a really bad day. I think this should be enough to show that, even in popular use, atomic weight is dead and buried. And, being a scientist myself, never heard about any textbook confounding weight and mass. This is an encyclopedia: the commerce usage should be noted, it's a reality in itself, but in the scientific definition (wich is the one we are mading the article for) no ambiguation should be left. Tercer 23:07, 26 December 2006 (UTC)

Disambig

This needs to become a disambig. Or at least we need weight (disambugation). --Piotr Konieczny aka Prokonsul Piotrus Talk 21:12, 22 October 2005 (UTC)

Deleted - a centripetal accleration field

I deleted the phrase "a centripetal accleration field" refering to gravity. I don't know why this is in there, but it makes no sense to me. What is a "centripetal acceleration field" ? And why does that make anything clearer? Fresheneesz 02:50, 17 April 2006 (UTC)

Oops-History clarification

I wasn't logged in when I made the alterations at 12:24, 17 Apr 2006, (Changed definition to note common usage. Corrected definition of physical science usage to that currently accepted in physical science---i.e. depends only on gravity, and directed downward.)--Alma Teao Wilson 03:10, 24 April 2006 (UTC)

It might be helpful to emphasise that the original (and to my mind correct) FPS unit of force was the poundal, not the pound, being the force equivalent to a mass of one pound accelerated at one foot per second per second.

Use of pound instead of poundal was simply a careless colloquial mistake.

Not really. It's use was usually intentional. The use of the pound-force predates the use of the poundal (invented ca. 1879), though the pound-force wasn't ever a well defined unit until the 20th century, and even today it doesn't have an official, universal definition as the corresponding kilogram-force does (it is 9.80665 newtons). Gene Nygaard 13:04, 5 August 2006 (UTC)

Pound convert

Okay, I've been watching the pound discussion for years now (2 to be precise), and I'm pleased with the article that they have now with regards to mass vs weight (I will always use weight as the force acting on an object due to gravity in this post). I think the real discussion on mass vs weight belongs here. So, as an initial informational post, here I add my two bits (well, more like 50 bucks) of thinking about this for two years.

  1. The layman, on average, knows the difference between mass and weight (I did a "scientific study", which proves nothing, but in my sample, the numbers are statistically significant
  2. Officially, the pound is a unit of mass. Many similar units (ton, ounce) are as well. This has been defined by several standards bodies. Technically it's official.
  3. Many people use pounds when they are thinking of weight, mostly they are unaware that de jure pounds is mass. In the US, pounds (et al) is the de facto standard.
  4. in many cases the usage of these terms is unimportant. ("What size of cereal box did you get?" "I got the 24 oz package." i.e. Even if they are thinking (if only subconsiously) "force" and the government regulates the "mass" of the box. Everything still resolves correctly.
  5. Even though it isn't technically correct, many "scientists" and non-laymen, still fall into the same trap. I've seen in textbooks targetting ages 10-30 mentioning something like "if you weigh 100 pounds on earth, you will weigh about 40 pounds on Mars." These are people who should know better, and are used to show the distinction between mass and weight, but can't keep the units correct. These kinds of documents have contributed to the laymen's usage. (Official government-sanctioned textbooks for use in public schools, and publications such as LIFE).
  6. Theoretical Physics books (for example The Elegant Universe by Brian Greene, page 148), with authors who have to know the difference, continue to perpetuate this technically incorrect, usage (Brian Greene mentions the Planck Tension (clearly a unit of force) and provides an estimate for it's value, expressed in Tons (technically a unit of mass)).

I'm comitted to ensuring that Wikipedia maintains this point of view. Sadly, I don't have the energy to really watch this page. If anyone would like a copy of my (non-wikipedia worthy) studies, I would be willing to provide them. More in-depth references on any of these things (which are wikipedia worthy, are available on request. The best way to obtain this information would be by leaving me a message on my talk page.

McKay 07:28, 15 August 2006 (UTC)

I'm not certain item #5 should be regarded as a mistake. It's clear from context that they are referring to a force due to gravitation. There would be an improvement in clarity if they had used newtons, certainly. --Yath 14:03, 15 August 2006 (UTC)
Yes, they are referring to a force. That's exactly what I'm saying. Canonically, the Ton is a unit of mass, and shouldn't be used in force calculations, the ton-force should be used. McKay 18:46, 15 August 2006 (UTC)
But it is also used as a unit of force, so it can't be "incorrect". The government's pronouncement doesn't override common usage. --Yath 19:58, 15 August 2006 (UTC)
Yes, and that's exactly what I'm trying to say. It's not just laymans usage, it's common usage. McKay 02:14, 16 August 2006 (UTC)
Let's tweak your wording a bit. I'd put it more like this:
1. The layman, on average, knows the difference between the amount of stuff they have and force due to gravity. Both mass and weight are ambiguous terms, with several meanings each.
2. Officially, the pound is a unit of mass. Many similar units (ton, ounce) are as well. This has always been true, ever since pounds were first used.
3. Many people use pounds when they are thinking of weight, mostly because the weight they are concerned with is the very same thing as mass in its physics jargon meaning.
4. In many cases the usage of these terms is unimportant. ("What size of cereal box did you get?" "I got the 24 oz package." i.e. Even if they are thinking (if only subconsiously) "force" and the government regulates the "mass" of the box. Everything still resolves correctly, unless you happen to be talking about a 400-ounce bar of platinum or something like that—even for those who misunderstand the meaning of "weight" in this context, who are in many cases those with a high degree of education in the sciences. You'd think that the fact that there is nowhere on Earth where newtons are legal for this purpose, and that everyone (even most labels in the U.S.) uses grams and kilograms, would be a big clue, but some people can think of all sorts of ways to ignore the obvious.
5. Even though it isn't technically correct, many "scientists" and non-laymen, still fall into the same trap. I've seen in textbooks targetting ages 10-30 mentioning something like "if you weigh 100 pounds on earth, you will weigh about 40 pounds on Mars." These are people who should know better, and are used to show the distinction between mass and force, but can't keep the quantity being measured straight in their minds, and thus use correct units. This would be true if we were talking about pounds-force, but in most cases in which people measure their weight, as in the medical sciences and in sports, pounds-force are not proper units for it.
6. One pound-force and one ounce-force and at least three different tons-force do exist. So do kilograms-force (and a megagram-force is one of the tons-force just mentioned), though since they are not a part of the modern metric system, the International System of Units, their use has been deprecated since 1960. There are, however, no troy pounds-force nor troy-ounces force. Unlike their avoirdupois cousins, and unlike grams and kilograms, the troy units of weight never spawned a unit of force of the same name. Gene Nygaard 22:16, 19 September 2006 (UTC)
Note that point '1' above appears to be one person's reporting of a unofficial survey, with a result that a statistically significant group of respondents apparently identified "weight" as a phenomenon of force as opposed to mass. Why should that observation need re-wording? (You speak of ambiguity in the possible interpretation of the term "mass". Could you please elaborate on that?)
In point 3, the argument was being made that many people have been persuaded, for better or for worse, to buy in to the notion that the term "pound" really does refer to a phenomenon which varies according to the gravitational field surrounding an object. This is probably due to the perpetuaton of factual misinterpretation such as what's pointed out in (5).
Some government bodies specifically state that the term "weight" is simply loaded with too many conflicting interpretations to be considered appropriate for "official" documentation. In Canada, the legislation defining systems of measures acknowledges that term "weight" appropriately refers to the same physical phenomenon as "mass". But the same legislation then goes on to state that the term "weight" should be avoided wherever possible in all government-issued documentation due to ambiguity of the layperson's interpretation of meaning, and explicitly replaced with either "mass" or "force".24.89.207.7 03:00, 28 February 2007 (UTC)

Mechanics

If someone wants to split off a Weight (mechanics) article for the usage common in mechanics, fine. Or whatever disambiguation is appropriate; not Weight (physical sciences), however, since things like molecular weight remain in such general use in the physical sciences.

If it were split off, the primary disambiguation needs to remain at the most general and often-used meaning.

Just be sure to take the dozen or whatever links along with you, from the "what links here". Gene Nygaard 14:59, 29 September 2006 (UTC)

I don't think that would be a good idea. Mechanics already has a version, acceleration due to gravity, and, despite intentions of some here to eliminate scientific rigour, even in the "popular" version there should be the truth displayed. This is a encyclopedia after all, not some popular term glossary.Tercer 23:03, 26 December 2006 (UTC)
It has nothing whatsoever to do with "scientific rigor". It has to do with the quite proper and legitimate use of the English language. There is no lack of rigor in using "weight" in the meaning used in commerce; it is in fact more rigorous that usage in science in general. It is never a force. The mechanics jargon usage, for example, is not the scientific usage in "molecular weight" and the like.
OTOH, saying that an article about acceration is the mechanics version is an extreme case of lack of scientific vigor. Gene Nygaard 15:34, 8 January 2007 (UTC)

"Surface" Gravity of Saturn citation

http://library.thinkquest.org/C001245/OrbitPc.html

Centrifugal Force

I replaced the example of reduced apparent weigh from centrifugal force to the effect of buoyancy. I think this is quite abstract to the casual reader; being immersed on a pool is a experience that everyone can recall. Furthermore, the case of earth rotation is explained in apparent weight, wich is linked. Tercer 23:50, 26 December 2006 (UTC)

Weigh or Weight?

I'm confused, is it weigh or weight? overweigh or overweight? What's the story of those two identical / homophon-homonim words? —The preceding unsigned comment was added by Bennylin (talkcontribs) 18:52, 6 February 2007 (UTC).

The noun is always "weight". And "weigh" is a verb, meaning to have weight or to determine the weight of something; that is often misspelled in Wikipedia articles and elsewhere. However, "weight" can also be a verb, with a different meaning. Try wiktionary:weight and wiktionary:weigh. Gene Nygaard 21:08, 18 February 2007 (UTC)

Irrelevance?

I was reading this article, and it was talking about how weight is used to measure how fat someone was. Then it got off on a tangent about americans, which to me seemed somewhat irrelevant (whether they are or aren't)

Im not suggesting it be removed, but maybe just put in a different place in the article. —The preceding unsigned comment was added by 158.59.229.189 (talk) 16:59, 1 March 2007 (UTC).

Weights of planets (relative or not) irrelevant here?

Shouldn't a list of weights of planets more properly belong in Planets or Solar System? --SV Resolution(Talk) 13:38, 27 July 2007 (UTC)

Should mass versus weight get its own article?

There is currently a discussion about how much detail on the difference between mass and weight should rightfully be in kilogram. If any regular editors are interested in that issue, please comment on the issue in the Request for comments. However, what I really want here is opinions on whether or not there should be a separate article at mass versus weight or if lots and lots of articles pound (mass), kilogram, gram, weighing scale, mass, tonne, ton, ounce and many more should simply link to this article (as many do already). I'm planning on expanding the mass and weight section here if editors don't think it needs its own article.

I can see above that there has been a lot of discussion about how to present the issue of mass versus weight, but I think this is a different issue; should it have its own article, or be here? Enuja 22:02, 20 August 2007 (UTC)

I'd think this is a good place—as long as it isn't built upon a false premise that there necessarily is a "difference between weight and mass".
Both words, of course, are ambiguous words with several different meanings. Often, in many contexts, including the overwhelming majority of articles linked to this one, they mean the same thing. At other times, we need to distinguish between them. What we need here is good information about both cases. Gene Nygaard 16:02, 11 October 2007 (UTC)
Yeah, I'd go along with Gene here. The current article does not appear to acknowledge the existence of the traditional use of the term "weight" to mean "quantity of matter" (that is, mass). That's a defect. --Trovatore 19:21, 21 October 2007 (UTC)
Especially since that's the weight which well over 90% of the incoming links to this article deal with, even though there are also separate articles about various more specific types of weight with that meaning with lots of links of their own. Gene Nygaard 13:25, 22 October 2007 (UTC)

Gene’s arguments are without proper foundation. This article is quite correct. Encyclopedia Britannica very simply defines “weight” as “[the] gravitational force of attraction on an object, caused by the presence of a massive second object, such as the Earth or Moon.” Wikipedia’s Weight article defines weight as follows: In the physical sciences, weight is a measurement of the gravitational force acting on an object. World Book (print edition) says this under Weight: Weight is the gravitational force put forth on an object by the planet on which the object is located. Further, the Kilogram article adheres perfectly to Encyclopedia Britannica’s discussion of the distinction between “weight” and “mass”. The article also gives proper and fair treatment to the fact that the term “weight” in common vernacular can occasionally mean “mass.”

With regard to Encyclopedia Britannica’s article on weight he’s written on Talk:Kilogram that we shouldn’t “stoop” to their level and he’s also written that Wikipedia’s own article on weight, which is linked to in several places in this article can’t be trusted. His attempts to redefine reality are bogus. Greg L (my talk) 16:34, 23 October 2007 (UTC)

I don't think he's trying to "redefine reality", just take note of the fact that the word "weight" has historically often been used, not merely "in the vernacular", to mean "mass". And, in some contexts, continues to be. That's just a true statement about the language; there's no physics content to the dispute. --Trovatore 17:06, 23 October 2007 (UTC)
If he limited himself to just that point, that would be fine. However, he has been active in trying to omit the term “weight” and replace it with “force due to gravity” in Kilogram notwithstanding that “weight” has a clear and unambiguous meaning in the physical sciences, and all other encyclopedic treatments are equally unambiguous. Greg L (my talk) 17:17, 23 October 2007 (UTC)

This subject is currently being discussed at Talk:Kilogram: Location for “Mass versus weight”. A consensus has been so far achieved that the section Kilogram#Mass versus weight should be moved out of Kilogram. Consideration is being given as to where to move it to. Options are to move it to Mass, or to Weight, or to give it its own article, Mass versus weight that all other articles can link to. If you would like to express an opinion on this matter, please click here. Greg L (my talk) 18:45, 8 November 2007 (UTC)

Slight wording confusion?

It's a very minor point, but should "So, if object A weighs, say, 10 times as much as object B, then object A's mass is 10 times that of object B" actually read "So, if object A has 10 times the mass of object B, then object A's weight will also be 10 times that of object B"

As weight is the factor that is dependent on mass (and gravity) and not the other way around?

138.38.149.112 (talk)

POV-pushing

I just wanted to note that this article, as currently written, pushes a specific, narrow point of view in its opening paragraph. Yes, in the physical sciences, the meaning of weight is generally restricted to a type of force. But in general, weight is a synonym for mass and always has been. The article's focus on a narrow point of view in its first paragraph is inappropriate. --169.236.9.80 (talk) 21:10, 9 April 2009 (UTC)

Agree. The section on measuring weight is getting to the point of being contrived. 'Weight' is a term that has been around in English for centuries; 'mass' only entered the language post-Norman Conquest. Meanwhile, the devices used to measure "weight" (like spring scales, which require precision manufacture) have only been around for about a century and a half at most. By contrast, the mass-measuring devices like the balance scale have been around for millennia. So there's a conundrum: a technology has existed for centuries to measure a concept that was "nameless" in English a millennium ago all the while a term existed for centuries for a concept that has only relatively recently been conceived of, much less ways developed to actually measure it. This ludicrousness is seen in the measuring section: "The standard masses [of a balance] are often referred to, non-technically, as "weights"." And the height of lunacy comes with this sentence: "Some balances can be marked in weight units, but since the weights are calibrated at the factory for standard gravity, the balance will measure standard weight, i.e. what the object would weigh at standard gravity, not the actual local force of gravity on the object." Ah yes, a thousand years ago everyone got their weights from a factory where they were calibrated to standard gravity...
The fact of the matter is that people have been measuring what they called "weight" for centuries and were using a balance scale to do it. The physical sciences today call it mass but back then it was called weight (and still is by most people). The confusion exists because somewhere along the way the concept behind the term 'weight' got changed or modified to mean something it could never have historically meant: a force.
What this and/or the article on mass vs weight needs is an historical overview of it came to be that "weight" ceased to mean mass and came instead to mean a force. Then, and only then, can the weight-mass confusion (sorry) be properly explained. D P J (talk) 18:34, 17 January 2010 (UTC)
Prior to the scientific disentanglement of weight and mass, I imagine that people were aware of the "weight" of something primarily because of the force that gravity exerted on it (as opposed to, for example, what we would now call its intertial mass). Therefore, I don't see any reason to believe that, at any time in history, "weight ceased to mean mass and came instead to mean a force". 86.172.96.114 (talk) 18:11, 25 January 2010 (UTC)

so is it a force or not?

how can it be force, if it is a scalar?

it says: "weight of an object is the magnitude, W, of the force that must be applied to an object in order to support it". —Preceding unsigned comment added by 94.194.101.43 (talk) 17:28, 17 July 2009 (UTC)

Opening definition

Currently the article says:

"The weight of an object in static equilibrium equals the magnitude of the gravitational force acting on the object, less the effect of its buoyancy in any fluid in which it might be immersed."

Should this also be less the (latitude-dependent) centrifugal force resulting from the Earth's rotation? 86.134.43.54 (talk) 00:37, 24 January 2010 (UTC)

No - the effects of the centrifugal force have already been taken into account by the earth being an ellipsoid rather than a sphere - as a result the gravitational force varies on the Earth - it is about 0.5% higher at the Poles than the Equator. Martinvl (talk) 07:29, 24 January 2010 (UTC)
No, that's a different effect. There are two things going on here: the ellipsoidal shape of the earth, which actually makes the gravitational force less, and the centrifugal force that diminishes the apparent effect of the gravitational force that is exerted. 86.161.42.192 (talk) 14:31, 24 January 2010 (UTC).
We could replace the words "gravitational force" by the words "measured gravitational force". This will take into account centrifugal forces as it will lump all the forces acting on the obejct apart from bouyancy into a single force.. —Preceding unsigned comment added by Martinvl (talkcontribs) 15:21, 24 January 2010 (UTC)
Forget buoyancy! It doesn't decrease the weight of ANYTHING; all it does is affect local scales of small area. It's like a harness hooked to a crane; it simply distributes the weight to a larger area, so that perhaps it's not measured, if you use a small area scale. But it all still there if you look at all the area. For example, you can float in a child's plastic pool and put as much weight as you like on a submerged watertight bathroom scale underneath you. But if the pool itself sits on a larger scale, that larger scale goes up by the amount of your total weight as soon as you climb onto it, and it doesn't matter what you do in the pool. All you're doing when floating is distributing your weight over the pool bottom, where the pressure all goes up just enough to make up for it (divided by the pool bottom area). The same is true of a balloon-- if it's a 1000 kg balloon the total air pressure times surface area underneath it goes up by 1000 kg when you blow it up and it flies. It has the same weight but not concentrated any more.SBHarris 20:05, 30 May 2010 (UTC)
I'm not keen on that. There seems no reason why "measured gravitational force" wouldn't also take into account buoyancy. 86.134.13.125 (talk) 23:49, 24 January 2010 (UTC)
OK then, "gravitational force as measured in a vaccuum". In the case of a body with a density of 1000 kg/m³, then by Archimedes Principle, the buoyancy due to air reduces its apparent weight by about 0.1%, air having a density of about 1.2 kg/m³. Put the same body intowater andit will lose all of its apparent weight (ie it will float). Martinvl (talk) 06:32, 25 January 2010 (UTC)
The "true" gravitational force acting on a body is identical whether it is in a vacuum, in air, or in any other fluid, so the term "gravitational force" in "gravitational force as measured in a vaccuum" presumably actually means "weight force". Thus, by using this wording, we would effectively be saying "The weight of an object equals its weight in a vacuum less the effect of its buoyancy in any fluid in which it might be immersed." which is probably not what we want. 86.140.131.81 (talk) 14:47, 25 January 2010 (UTC).

Weight is (minus) the force F= ma necessary to push an object of mass m from free-fall into an accelerated frame a that differs from free fall by the proper acceleration a. The reason for the minus sign is that weight and the force which produces proper acceleration (same as g-force) are an action/reaction pair, and by Newton's third law are equal and of opposite direction. SBHarris 03:13, 30 May 2010 (UTC)

"Weight" and "Apparent weight": Contradiction and Confusion

This article says that "weight" is lessened by the effect of buoyancy. This contradicts Apparent weight, where "weight" is said to be purely the gravitational force (i.e. excluding things such as buoyancy). We need some experts to focus their attention on these two articles and decide, of all the forces and accelerations acting on a body in a gravitational field (in particular a body at the surface of the Earth), which contribute to the object's "weight" and which do not. As well as gravitational force, these include:

  • Buoyancy (in air or other fluid). For example, what is the weight of a helium balloon? What is the weight of a floating piece of wood?
  • Centrifugal force (on spinning Earth).
  • The effect of accelerations, such as in a lift. For example, consider astronauts in orbit. What is their weight? If it's zero then this implies that the weight of someone in a free-falling lift is zero, and that their weight in a lift accelerating downwards at 0.5g is half their normal weight, which undermines most of the supposed distinction at Apparent weight.
  • Any other miscellaneous forces, such as magnetism.

The factors that do not contribute to "weight" presumably explain the difference between "weight" and "apparent weight". If all the forces and accelerations acting on a body contribute to "weight" then presumably "apparent weight" is a bogus concept. 86.136.27.202 (talk) 21:03, 2 February 2010 (UTC).

You are correct-- apparent weight IS a bogus concept. There is only weight. Weight is a vector W with magnitude -m * (g-force).
\vec{W} = - m \vec{g} Where the vector-g is the g-force. SBHarris 22:46, 29 May 2010 (UTC)

Weight and mass are Not the same thing

Ok, I don't know who has been writing this stuff but it makes no sense !!! now there's a "how to convert" section between mass and weight !!!!. Firsttly mass is an scalar, weight is a force then a vectorial magnitude (then you have to specify the direction !!!). I'm an Engineer myself, and there's nowhere such non sense as Force=mass*acceleration/acceleration ... Does it make any sense???.

You cannot convert scalars into vectors and viceversa plus weight and mass are not equal in magnitud nor in units!!! I'm going to look for the right tag for this complete mess of an article, this is very basic stuff and it should be there with no fault.—Preceding unsigned comment added by 190.28.82.12 (talkcontribs) 02:12, April 13, 2010

It appears that you know a great deal more than I do about the subject!  :) Be that as it may, I think it's more appropriate to work on correcting the article and not labeling it a 'hoax'. There might be inaccuracies in the article, but that doesn't make it a hoax. I think the article would benefit from your knowledge in correcting it - if it needs it. Also, please sign your posts in the talk page.  :) Wikipelli Talk 02:43, 13 April 2010 (UTC)
The conceptual errors are so evident and spread everywhere that the article needs full rewriting. It is just plain wrong.
The article is absolutely misleading to the unaware reader. It's not a phrase or a word but the whole article that needs to be re-written from scratch; The reason for having tagged the article straight away is basically for impeding that such wrong information is spread. I recognize, however, that the word "hoax" is perhaps a little strong and that maybe is not the needed tag, I will replace for dispute tags instead.—Preceding unsigned comment added by 190.28.82.12 (talkcontribs) 02:55, April 13, 2010
I cannot promise that I'll edit the article. (unlike 5 years ago I find it boring, that's why i log in as anonymous). someone else can do it.—Preceding unsigned comment added by 190.28.82.12 (talkcontribs) 03:27, April 13, 2010
I am not a user so can't do this signed, but W is a vector, m is a scalar, and g is a vector. The mass is the coefficient that scales the acceleration due to gravity. This is perfectly acceptable. —Preceding unsigned comment added by 131.227.156.133 (talk) 16:17, 19 April 2010 (UTC)
Question to 190.28.82.12: Can you give a citation of a reliable source that states that weight is a vector quantity and not a scalar?  --Lambiam 21:06, 26 April 2010 (UTC)
And another question: when you put the (grossly inappropriate) {{Hoax}} tag on the article, it stated clearly: "In modern scientific usage, however, weight and mass are fundamentally different quantities". So what is the content of your gripe that "weight and mass are not the same thing"? I did not see any evident conceptual errors, so maybe they are not so widespread and evident as you claim. Rather than ranting how egregiously bad the article is, can you point out specific shortcomings that are not in line with present-day mainstream insights in physics?  --Lambiam 21:26, 26 April 2010 (UTC)
We don't really a need a source for that. Of course weight is a vector and mass is a scalar. And of course we cannot "convert" scalars into vectors and vice versa, and of course weight and mass are not equal in magnitude nor in units. But to every mass (scalar) there corresponds a weight (vector) that can be found by multiplying the local g-acceleration vector with the mass. And likewise, to every weight vector, there corresponds a mass that can be found by dividing the magnitude of that weight vector by the magnitude of the local g-acceleration vector. DVdm (talk) 21:29, 26 April 2010 (UTC)
Who is "we"? Maybe you don't need a source for things that are "of course" so, but Wikipedia does. The IP who is currently "correcting" the article also apparently thinks that their definition of weight is of course correct and has not supplied a source, but as you can see below at least one editor, who is a researcher in theoretical physics, disagrees, and the only acceptable way of resolving the issue is by reference to reliable sources. How "of course" is it really that weight is a vector? Most sources that I have consulted are ambiguous, some define weight unambiguously as a scalar (as in: "... is the magnitude of the vector ..."), and some, after stating that it is a vector, treat it consistently as a scalar (as in "when an object is moved from the equator to the North Pole, its weight increases by about 0.5%"). Clearly this is not an open-and-shut case.  --Lambiam 15:02, 27 April 2010 (UTC)
Sure. See Martinvl's comment in the ISO-section. Nothing much to add. In physics, weight is a vector and mass is a scalar. In everyday language the kilogram is used as a unit of mass and as a unit of weight, although we (yes, we, again) know that weight should be expressed in Newtons. That's life, I guess :-) DVdm (talk) 16:25, 27 April 2010 (UTC)

Well, IP your current definition of weight is also wrong. The definition should something like "weight is the forces that a stationary object in a gravitation field exerts on its support." That, is weight and normal force form a reaction pair. In particular, this means that, yes, objects are lighter at high tide then they are at low tide. Alternatively, a functional definition of weight is "the quantity measured by a spring scale". TimothyRias (talk) 07:47, 27 April 2010 (UTC)

Correct! What went wrong is the failure to realize that "weight" is the counterforce (reaction force) to whatever force induces proper acceleration, which is the acceleration away from the state or path of free fall. That proper acceleration is the same as g-force. It is what an accelerometer measures. These concepts of (proper acceleration and g-force) are somewhat subtle concepts, but once grasped, weight is easy. For any mass, weight is simply the counterforce vector that points in the opposite direction to the proper acceleration, and differs from it by the factor of mass:
\vec{W} = - m \vec{g} Where the vector-g is the g-force.
There is no such thing as "apparent weight", or at least no place for it. There is just "weight." All the "short range" stuff is due to the fact that gravitation does not cause proper acceleration, or g-force, and isn't measured by an accelerometer. Thus, it contributes to g-force and proper acceleration only indirectly, via the mechanism that some mechanical force must induce g-force in a gravitational field, if the object is not in free-fall. And since every mechanical force exists as an action-reaction pair, the weight is the reaction force to that mechanical force.

Doing a read through the g-force article, which is finally correct, will help everybody here (also a read through the proper acceleration article, which is about the same thing, but more technical). The g-force for an object sitting on the ground is 1 g (9.81 m/sec^2), upwards. The proper acceleration is 1 g, upwards. The mechanical force that causes this proper acceleration is provided by the floor/ground, and is m\vec{g} (a vector force), upwards. Note that at this point the force of the floor could be due to the fact that it's supported by the Earth, or the fact that it's supported by a rocket moving upward at 1 g in space. We're in an accelerated frame either way, as required by the equivalence principle. Gravitation looks like being in a rocket.

The opposing downward force, which "explains" in this accerated frame why the object undergoes no coordinate acceleration, but is motionless (zero net force), is the weight. It's a fictious inertial force in a rocket, but it's provided by gravity on a planet. It is -m\vec{g}, a vector pointing downwards. Remove the floor (or let the elevator cable snap), and the coordinate acceleration now is non-zero (as the object goes into free fall), but the g-force, proper acceleration, and the weight, all now go to zero. We have weightlessness and zero-g (meaning zero g-force). It's actually quite simple once you start from the proper acceleration and "accelerometer-measured" point of view. SBHarris 23:11, 29 May 2010 (UTC)

<outdent>

Later. I see the problem, now. The ISO has decided to define "weight" in terms of the gravitational and fictious inertial forces, since they point in the "right" direction (the direction of the weight vector), rather than the proper acceleration forces, which point the other way, but are otherwise equal in magnitude SO LONG AS the object being "weighed" in the accelerated frame is accelerated along with the frame itself, which is a given in the definition, since it is assumed when it says the body IS IN the reference frame. That means the object has to be in contact with the floor of our accelerated elevator-- it can't be falling inside the elevator, or else it wouldn't be in the elevator reference frame, and would not satisfy the definition, which says it must be IN the reference frame, which means if our frame is accelerated, the body has to be accelerated with it.

"The weight of a body in a particular reference frame is defined as the force that gives the body an acceleration equal to the local acceleration of free fall in that reference frame" doesn't mean the body IS in free fall in that frame. It means this is the force (and direction) you'd need in theory TO PUT IT into free fall. That is exactly equivalent (but in the opposite direction) to what force you'd must have to move it from free fall into the accelerated frame in which you measure its weight. Which is the proper acceleration force, but with the opposite sign. So the definition of minus the m (g-force) is actually what NIST is saying. We don't have to worry about whether objects in free fall in a gravitational field still have "weight" because in the NIST definition, they do not. For example, if you drop an object down an elevator shaft, it IS in free fall, so there is NO force needed to give it "an acceleration equal to the local acceleration of free fall in that reference frame," because that's the acceleration it has already (as evidenced by the fact that indeed it is in free fall). Thus, no force is needed, therefore it has no weight. No object in free fall has weight, according to NIST. Voila. SBHarris 02:21, 30 May 2010 (UTC)

"local acceleration of free fall in that reference frame" refers to the acceleration with respect to the reference frame, the second time-derivative of position, expressed in the coordinates of that frame. The object has this weight in this reference frame, regardless of whether it is actually falling, or resting on the floor, being thrown, or whatever. If the reference frame is the Earth, the weight is equal to the gravitational force. For example, an astronaut has zero weight with respect to his orbiting spaceship, but with respect to Earth his weight is only a little less than on Earth.--Patrick (talk) 08:14, 30 May 2010 (UTC)

No. You didn't read the definition and have it exactly wrong, and you screwed it up in the article as a result (please use this talk page, before writing that the NIST has conflated some definition with your pet one, and that ISO's definition of weight is observer-dependent, making the ISO a bunch of boneheads). An object does NOT (repeat not) have its weight in the free-fall reference frame that is (or may be) accelerated with regard to it. It has weight in its own reference frame where the scales are (call this frame A, the object and scales frame), and this weight is calculated (according to the ISO definition) by looking at the coordinate-acceleration of a DIFFERENT reference frame B which represents the acceleration of "free fall" in the object's frame A. THAT definition is observer-independent, which is as it must be, because all observers must measure the same weight for an object (it's sitting on a bathroom scale-- do you really think different observers see that scale read a different NUMBER?? No, they don't.) "Weight" only has meaning in the frame where the object resides. It is caused by the object's mass and its proper acceleration, which is Lorentz-invariant, which means of course observer-independent. As it must be. SBHarris 19:52, 30 May 2010 (UTC)

Before accusing specific editors of "screwing it up", perhaps you should examine which editor made which changes. At the time you wrote this, User:Patrick hadn't touched the article since June 24, 2005.  --Lambiam 08:03, 31 May 2010 (UTC)
Actually, from what the NIST source says about the ISO definition it makes reference to "a particular" (implying arbitrary) reference frame. (I still want to see what ISO 80000-4 says exactly) This would very much imply that the ISO definition makes weight a reference frame dependent quantity. This makes sense, since depending on the reference frame it reduces to either the operational definition (in the scales rest frame) or to the "gravitational" definition (in the Earth's or the Sun's rest frame depending on the exact interpretation of the gravitational definition). This is good way of ending a "dispute" going back for at least 40 years.TimothyRias (talk) 06:12, 31 May 2010 (UTC)
There is an earlier almost identical ISO definition (International Standard ISO 31-3. (1992). Quantities and units. Part 3, Mechanics – now withdrawn) which can still be found here. The definition is as follows:
"The weight of a body in a specified reference system is that force which, when applied to the body, would give it an acceleration equal to the local acceleration of free fall in that reference system"
I don't think the change in wording with the present standard – which I'd also like to see – such as "specified" → "particular" and "reference system" → "reference frame", reflects a change in intention. What is really interesting is what is stated in the Remarks column adjacent to this definition:
"When the reference system is the Earth, the quantity defined here has commonly been called the local force of gravity on the body. It is noteworthy that this weight comprises not only the resultant of the gravitational forces existing at the place where the body is, but also the local centrifugal force due to the rotation of the Earth. The effect of atmospheric buoyancy is excluded, and consequently the weight defined is the weight in vacuum."
This shows conclusively that the ISO definition is not meant to be equivalent to the gravitational CGPM definition of F = mg.  --Lambiam 08:03, 31 May 2010 (UTC)
Actually, it does not as in many cases the local acceleration due to gravity g actually is meant to include the local centrifugal force. (For example when it features in the discussion of pendulums.
Also whether the ISO definition includes local centrifugal force depends on exactly what frame you choose. In a corotating frame with the earth it is included, but if you would take a sidereal frame it would note be. This again shows the flexibility of this definition.TimothyRias (talk) 09:01, 31 May 2010 (UTC)
No, that's quite wrong. The influence of rotation on the weight of an object on Earth is the same, no matter what frame you look at it from, co-rotating or not. You're saying something like the weight of an object in a centrifuge (ignore the Earth's gravity for a second) depends on whether you co-rotate with it or not. No. Only the names you have for the origin of the forces change, but the forces and weight do not. If you co-rotate, the weight is due to a fictitous "centrifugal force" that appears in your frame and drives the object into the centrifuge bottom, and that is its "weight." Of course, the bottom of the centrifuge must supply a counterforce, or else the object would break through it. If you do not co-rotate, you see the situation as an object wanting to fly off in a straight line, and only prevented from doing so by the centrifuge floor, which applies a centripetal force which makes it go in a circle, instead. Again there is a counterforce to this centripetal force, and THAT is the weight. But the two weights are just the same.

On earth, it's the same situation. If you co-rotate, you see a centrifugal force lifting objects upward, and making them lighter to a spring scale. If you don't co-rotate, you see that gravity supplies a part of the centripetal force to make them go in a circle, and thus there is less gravitational force to make them heavy (press down into the earth), so again less weight. To see that clearly you can think of what would happen if the Earth were spinning fast enough to put things on the equator in orbit-- in that case the entire centripetal force would be supplied by gravity (as seen from non-co-rotators) and weight would be zero because none would be left to cause weight-- it has all gone into causing circular motion and none is left to cause weight. For rotators, the tremendous centrifugal force would lift things off the ground completely, and again weight would be zero. This is a frame independent thing. The only way to make weight frame dependent, is to talk about different frames and different physical situations, not different observers for the same physical situation. These are not the same. SBHarris 09:42, 31 May 2010 (UTC)

Wrong according to your pet definition maybe. But the 1992 ISO definition (as linked above) makes it very clear, that weight should be measured w.r.t. a specified frame of reference. This means that although the weight of an object in a centrifuge changes wrt its comoving frame, it does not wrt the laboratory frame. TimothyRias (talk) 09:59, 31 May 2010 (UTC)
"The weight of a body in a particular reference frame is defined as the force that gives the body an acceleration equal to the local acceleration of free fall in that reference frame." That does not say that the weight of the body (in frame A) is any different if measured from some other frame; it only says it's defined as a certain measure when you're in the object's rest frame. As a practical matter it's easiest to weigh an object when you're in the rest frame of the object (the accelerated frame that produces the weight) but in theory you could be in others, so long as you're talking about the same physical quantity and same physical situation. Yes, weight is a quantity that only makes sense only WRT a particular accelerated frame, which is why things weigh differently on the Earth vs. the Moon, or on Earth vs. on Earth in an Elevator. But those are different physical situations, so you're looking at different experients, not merely the same experiment as seen by different observers. An object sitting on the Earth has the same weight (with regard to the Earth rest frame) whether I as an observer go by at a million miles an hour, or go by in free fall. That's not true of an object's clock rate or its length as I look at the same clock in different frames. These are two different senses of the idea of "frame dependent." Weight in an object's rest frame is something it "has" (the force exists as a real thing, and can be measured by an accelerometer or scale in that frame), and it is that 4-force that all observers (people in other frames) see as the same. An object's length, however, is NOT something it "has." Again, if you want to talk about the object's theoretical weight IN OTHER FRAMES you've not just changed observers, but changed experiments/situtations. SBHarris 18:30, 31 May 2010 (UTC)
You're talking a somewhat fundamentalistic operational approach to defining weight. You are entitled to that opinion, but it is not what the ISO definition is saying at all. Note that the actual text of the ISO definition talks about the weight of an object "in a specified frame", not about the weight of an object in its rest frame or the weight of an object in a comoving frame. It is clear that it means any frame in general. The remarks in the ISO definition also explicitly note that this definition is equivalent to the "gravitational one" if one talks the Earth's rest frame as the chosen frame. Now, of course, you are entitled to your opinion that that definition is wrong, but that is completely irrelevant to this article.TimothyRias (talk) 21:32, 31 May 2010 (UTC)
On the contrary, the "remarks" obviously assume that the object is at rest in the reference frame, or else the remarks would have had to address the two separately, yet do not. Instead they only address the frame, and assume that you understand that the object is at rest within it. Where else would it be? If it wasn't at rest in the frame described (the rotating Earth's surface), the remarks about it would be incomplete, or simply wrong. ""When the reference system is the Earth, the quantity defined here has commonly been called the local force of gravity on the body." Do you see anything there about motion of the body within the frame? If it is in free fall in an Earth-centered frame, would the statement in the remark have any way of being correct? No. The statement can only be true if the object is at rest with respect to the Earth, as well. By extention, it is clear that the ISO is always talking about object and frame at the same time; it cannot be any other way. SBHarris 02:00, 1 June 2010 (UTC)
Sorry, but you are way of base here. The motion of the object is completely irrelevant to the ISO definition, it only references the local acceleration of free fall at the object's current location. The remark in the statement would be perfectly correct if the object were in free fall, riding a roller coaster or spinning in a centrifuge, the local force of gravity on a body is not effect by the body's movement (Safely neglecting relativistic corrections). When an object is free falling, then in the refence frame of the Earth it is undergoing a (nearly) constant acceleration as the result a (nearly) constant force of gravity. Please, remember that the concept of gravity is frame dependent in the context of GR (and also that the frame in GR is not uniquely determined by the physical state of a single observer, but rather by the physical state of a family of observers whose world lines completely cover a local patch of spacetime).TimothyRias (talk) 07:54, 1 June 2010 (UTC)

Arbitrary break

@Sbharris: You seem to think that in the phrase "The weight of a body in a particular reference frame" the phrase "in a particular reference frame" refers to "body", but I think it refers to "weight". Also, although a physical frame such as an elevator cabin can be a convenient reference frame, the two should not be confused, like you seem to do in text like "the force necessary to put an object in a particular reference frame into a free-fall frame".--Patrick (talk) 07:55, 31 May 2010 (UTC)
@Sbharris: Why should the ISO definition somehow be the "true" definition of weight, making the gravitational definition a "false" one? They are simply different definitions, produced by different institutions, and used by different textbooks. Weight as defined by ISO/NIST is precisely what is called "apparent weight" by more than a few textbooks. What exactly is the harm in pointing out that "ISO/NIST weight" is not "gravitational weight" but instead "apparent weight"? That is a useful clarification; how does it imply a suggestion of boneheadedness?
Also, the usual and time-honoured terminology "observer-dependent" goes back at least to Einstein (von einem Beobachter nicht unabhängig), and I think it is pedantry to insist that this should be "instrument-dependent". All measurements are "instrument-dependent", so in this context it then becomes a completely vacuous qualification.  --Lambiam 08:03, 31 May 2010 (UTC)
Well, let me put it this way: "observer-dependent" is generally used in relativity to talk about things we expect to change and change a lot, depending on the observer's frame (like spacial dimention and time-lapse-rate), and that these changes are NOT due to instrument error from one observer to the next, but really exist in reality. On the other hand, there are so called Lorentz-invariants that we fondly believe are observer-invariant, even though of course every observer will get slightly different values for (say) the charge of each new electron on a drop, or the speed of light. We put those down to instrument error. Unless you really think that all electrons might have slightly different charges, and the speed of light might REALLY vary a bit from one person to another? Hmmm? No sophistry, now. Weight, because it is connected (a least by the ISO) to the Lorentz-invariant 4-acceleration, 4-force, and proper acceleration is observer and frame independent. Which is good, because it can be measured directly by an accelerometer, which puts up a digital value if you like. Try that with measuring a distance or time interval! (You'll find your clocks and tape measures perverted in ways your scale never will be). What time it is, and how fast time passes, is something no observers in relative motion agree on. But how hard something presses on a scale they all MUST agree on. To believe otherwise would be to posit that a person is squashed into stawberry jam as seen by one observer, but is up and about, and feeling fine, as observed by another observer. That cannot happen. Being squashed into strawberry jam is an EVENT; all observers observe it.

I'm not married to the idea that ISO/NIST is god, but it's at least from 2006. I don't like the idea of using CGPM's definition only because it's more than a century old, and surely must be outdated. Good heavens, it dates from pre-relativity; what do you suppose their standards for length and time look like? Okay, so that ancient definition of "weight" and "standard weight" didn't take into account local centrifugal force or travel to other planets. I'm not surprised, since it's from 1901. The real quesiton is why pay any attention to it at all, except as history of Victorian beliefs and Victorian ideas? The ISO/NIST definition is what I'd like to call "weight" here-- it's -mass x proper acceleration. It might look like what is now in the "apparent weight" article (save for lack of attention to buoyancy error which the apparent weight article includes) but IOS/NIST is a definition of "weight" according to THEM. Who says otherwise, except the 1901 guys? I would put ISO down as the modern weight definition, and let the definition of "apparent weight" be decided by google. As noted, outside WP, the first entries I found for it were in reference to incorrect spring scale measurements due to buoyancy, and that's all. SBHarris 08:49, 31 May 2010 (UTC)

SBHarris, you might want to have a look at some of the sources cited in the article. According to a census of university textbooks taken in 2003 about 75% of them us the "gravitational" definition of weight. This shows that definition has clearly not fallen out of use. WP:NPOV requires the article to discuss both gravitational and operational definition without declaring one to be the "true" definition. (Also remember WP:TRUTH) TimothyRias (talk) 09:13, 31 May 2010 (UTC)
Furthermore, your additions – most of which, in my opinion, are not improvements – are largely unsourced and have the look and feel of OR. Could you supply citations to them? In some cases you also have modified a citation-supported statement so that the cited source no longer covers the extent of the statement; please try to avoid that.  --Lambiam 08:26, 31 May 2010 (UTC)
Sorry if I messed up an already cited thing, feel free to change it back in places I did. As for "OR" in the sense of doing your own math based on the English word definitions of ISO, we're all stuck with doing that, are we not? You say weight is observer-dependent, and it's clear to me that the ISO is only talking about one observer, and that the acceleration they're talking about is a Lorentz-independent thing (as are all measurable-accelerations in relativity). Here is where there's no escape from doing some physics for yourself. I've done more more of this than the people who wrote the article in the state I found it in! SBHarris 09:14, 31 May 2010 (UTC)
To me it is clear that the ISO definition is meant to be frame dependent. Since, I've probably done as much physics in my life as you, we need a source to settle the difference of opinion. TimothyRias (talk) 09:25, 31 May 2010 (UTC)
LOL, if you've done as much physics as I have, how come you make a mistake like the one I just corrected above? Phooey! ;) SBHarris 09:43, 31 May 2010 (UTC)
Maybe because I didn't make a mistake? Also, this type of personal attacks are quite unbecoming of seasoned editor like you. You should know better. TimothyRias (talk) 10:05, 31 May 2010 (UTC)
You did make a mistake by suggesting that an object in a centrifuge would have a different weight when seen by different observers. It would not, so long as you don't change the experiment. Suggesting you made a mistake is not a personal attack-- that's thin-skinned even for Wikipedia. And if you're going to suggest that the discussion of an editor's comparitive experitise is in the realm of personal attack, I'll simply point out that you started it, not me. If you don't like that road, don't go down it. SBHarris 18:34, 31 May 2010 (UTC)
Use of the terms like "LOL" and "Phooey" are personal attacks, and completely unbecoming of an editor of your age. Also, the only one making a mistake here is you, by not actually consulting any sources, and simply declaring your opinion to be truth. TimothyRias (talk) 21:36, 31 May 2010 (UTC)
Use of the terms LOL and phooey are intended to keep the tone from being offending or serious. But some people insist on being offended no matter what one does, and you may be one of them. That's too bad. SBHarris 02:01, 1 June 2010 (UTC)

Entry for "hyl" says it is obsolete

I don't get the three sets of mass/weight in the article. I learned that a pound measured weight, and a [kilo]gram measured mass - then that the customary unit of mass was the slug, and the metric unit of weight or force was the newton. —Preceding unsigned comment added by 208.127.183.91 (talk) 02:35, 15 April 2010 (UTC)

ISO 80000-4 (2006)

Anybody have access to ISO 80000-4 (2006)? This should contain the most up to date technical definition of weight as agreed upon for an international standard, which should be useful for this article. As far is I can infer from other sources the definition is something like:

the weight of a body in a particular reference frame is defined as the force that gives the body an acceleration equal to the local acceleration of free fall in that reference frame

This coincides with the more mundane definition I added to the article just now, although this more precise. (It avoids vague undefined terms such as support.) TimothyRias (talk) 08:38, 27 April 2010 (UTC)

I agree - a definition from an authoritative body generally stops a lot of rubbish being added and removed. For example, there was a lot of discussion as to whether or not a stone (14 lbs) was a mass or a weight. I eventually dug up a bit of UK legislation that said it was either a mass or a weight (written by politicians, advised by lawyers who probably didn't understand either). I quoted that verbatium (and added a "[sic]" to it). That killed the discussion. Martinvl (talk) 11:54, 27 April 2010 (UTC)
Does a body without support (i.e. in free fall) still have weight? The current definition in the lede does not apply, but I'd guess that, although it has no apparent weight, it still has weight, and in fact the same weight as if it was supported. Can't we simply define "weight" by stating: "The weight of an object is the gravitational force acting on that object." (or, if you will, "... is the force exerted by the local gravitational field on that object"), and then elaborate on the consequences of that definition?  --Lambiam 20:19, 27 April 2010 (UTC)
Well, apparently the ISO does not agree with you. TimothyRias (talk) 03:32, 28 April 2010 (UTC)
The definition you put in the lede implies that "the weight of an unsupported object" is a meaningless concept, whereas the source you cited in support would give it a weight W = 0. However, the cited source is only a "Letter to the Editor" giving one person's opinion, and not a peer-reviewed publication. Mr. Allen L. King's definition is actually the same as the definition currently given to apparent weight in Wikipedia, so if he is correct (as you implied he is), the notions of weight and apparent weight coincide! But now what does the ISO say? I'm sure they did not say "the weight of an object is defined as proposed by Mr. King in his Letter to the Editor of 1962" (not 1963, as you put in). Can you tell us what that definition is precisely, and in what scenario it assigns a different weight than the definition proposed by me? In the meantime, for an overview of how weight is dealt with in university-level physics textbooks – a majority of which (76%) would appear to agree with me – see: Galili, I.; Lehavi, Y. (2003). "The importance of weightlessness and tides in teaching gravitation". American Journal of Physics 71 (11): 1127–1135. doi:10.1119/1.1607336.  The majority follows the recommendation by Uri Gat that "in technical and scientific use, weight shall be restricted to mean force of gravity" (Gat, Uri (1988). "The weight of mass and the mess of weight". In Richard Alan Strehlow. Standardization of Technical Terminology: Principles and Practice – second volume. ASTM International. pp. 45–48. ISBN 978-0-8031-1183-7. ). --Lambiam 13:24, 28 April 2010 (UTC)
Good, you seem to have learned the importance of citing reliable sources. Not doing so can lead to any article being particularly POV. This article should work from the internationally established definition of weight not some single editor's preferred definition. As for what the ISO definition is exactly, as I don't have the ISO 80000-4 text, but the text I quoted above is from the BIPM reference in the article that is citing the ISO text as support. TimothyRias (talk) 14:43, 3 May 2010 (UTC)
Please don't be condescending, in this case for no good reason. As you can see above (at Weight and mass are Not the same thing), I asked for a citation supporting the edits of an editor and stressed in response to another editor that Wikipedia does need a source even for things that are "of course" so.
For the rest, how can you say that the definition from the NIST (not BIPM) reference ("the weight of a body in a particular reference frame is defined as the force that gives the body an acceleration equal to the local acceleration of free fall in that reference frame") coincides with the "more mundane" definition ("The weight of an object, is the force exerted by that object on its support")? They are essentially different, as becomes evident by considering a body in free fall, or on a swing, or on a support in the process of buckling, or an upside-down rocket firing full force with its nose embedded in solid bedrock.
In the theory of gravity, "the force that gives the body an acceleration equal to the local acceleration of free fall" is a complicated way of saying: "the gravitational force acting on the body". This follows immediately from the definition of free fall.
The complication stems from an apparent desire to avoid the term "gravity" and thus work around the Newtonian setting – in my opinion pointless, not only since you can simply interpret "gravitational force" in the setting of general relativity as the fictional force caused by the local curvature of spacetime, but particularly also because the notion of "free fall" is conventionally defined by reference to gravitational force.  --Lambiam 23:54, 3 May 2010 (UTC)
First of all, my apologies for being stingy. (I should not be posting in a state of sleep deprivation.)
The two definitions agree in the situations where the mundane one makes sense in the first place. That is in a frame in which the object is at rest, the force needed to give the object the acceleration of free fall, is the force that the object would exert on its support. (In this context any thrust should be considered part of the "support".)
Of course, from a purely GR point of view this is the gravitational force acting on the object in that frame. The problem is that a casual reader will not pick up the term gravitational force in the GR sense, but in the Newtonian sense; i.e. as the force from Newton's law. In this context, avoiding the word gravity in the definition of weight is a good thing. TimothyRias (talk) 13:06, 6 May 2010 (UTC)
Is it really such a good thing? In conditions where a "GR" definition makes a difference with that based on the Newtonian framework, one is typically not interested in determining or discussing the weight of objects. Most university-level physics textbooks use the concept of gravity in the definition, and in general many encyclopedia articles on classical physics concepts start with a Newtonian approach, and if necessary give a GR treatment as kind of an afterthought. Our article only succeeds in avoiding gravity in the first sentence of the lede. I'm not at all convinced it is a good thing to avoid the concept of gravity in the definition; in fact, I think it is not at all helpful, but instead confusing to the reader seeking enlightenment. I am further convinced that it is a bad thing to have a definition that is wrong except when the unstated condition is satisfied that the object be "at rest" – and talking about relativity, aren't all objects at rest in some coordinate system?  --Lambiam 15:42, 6 May 2010 (UTC)
About the last remark, yes all objects are at rest in some coordinate system, but in that coordinate system there will be a nontrivial acceleration of free fall at the location of the object (unless the object is free falling). As such all object have a well defined weight in their rest frame. It is this weight that the "support" definition (which only impicitly establishes a frame) defines and that agrees with the ISO definition.
The problem with including the term gravity in the definition of weight is that to most people this excludes centrifugal effects from the definition of weight. These are however included in the ISO definition. At least for frames that hold the surface of the Earth to be motionless, which the common frame for almost any Earth bound experiment. If the Earth was not rotating everything on Earth would be significant heavier (by a few percent).
I'm not married to current sentence in the lead however. I'm open to alternatives, but what ever we put as a first sentence needs to be backed by source. This is one of the reasons I asked if some one had access to the ISO 80000-4 text. TimothyRias (talk) 09:21, 7 May 2010 (UTC)