On Thu, 25 Sep 2003 01:16:33 GMT, Dave Shrader
wrote:



Gene Nygaard wrote:

[SNIP]


Apparently you are claiming that pounds are not units of mass.

Where did you learn that?

Well, I learned that a Pound is a unit of Force.
Well, I learned that a Slug [pound mass] is Pound*acceleration.
Well, I learned that mass is pound*sec^2/foot.

Where did I learn this? What's my source? Physics 101, University
Physics, Sears and Zemansky, Addison-Wesley Publishing, 1956, Chapter 6,
page 94.

I hope tou don't need another reference?

Now, what's your real problem? What are you trying to say?

Can you quote it to me, specifically where it says that pounds are not
units of mass? I'll bet you just misunderstood what it said. I have
the 1970 edition of Sears and Zemansky myself, so I'm betting that if
anything, what it actually says is clearer in that older edition than
it is in the 1970 edition.

Pounds force do exist, of course. What I'm asking you to show me is
not that, but rather that pounds are not units of mass.

Sears and Zemansky didn't lie about this in 1956. They might have
been dishonest and deceptive about it, not concerned enough about the
possibility that fools like you would misinterpret what they said or
actually encouraging such misinterpretation. But they didn't lie
about it. Some textbooks today might actually lie about it (or,
alternatively, their authors are too poorly educated to know any
better--take your choice).

Gene Nygaard

Dave, W1MCE



Being the skeptic that I am, how can I convince myself that that is
true? Is there some textbook, or something from some national
standards agency, that would help me verify this?

Gene Nygaard

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/

On Wed, 24 Sep 2003 21:04:11 GMT, Richard Clark
wrote:

On Wed, 24 Sep 2003 20:15:51 GMT, Gene Nygaard
wrote:


A balance, by implicit definition again, consists of comparing two
masses under the influence of Gravity. Given it is a bridge, in a
sense, the constant of Gravity is discarded from both sides and mass
is compared only. It is a convenience of earthly expectations (and a
defunct system of measurement) that the scale is marked in pounds.

The matter of convenience is in the other direction, stupid; we're
willing to substitute cheapness for accuracy in what we want to
measure on those unreliable bathroom scales. They aren't any more
accurate for measuring force than they are for measuring mass on
Earth; haven't you ever weighed yourself on your mother's scale or
somewhere else and found it differed from yours at home by several
pounds? Do you automatically assume you've gained or lost that much
weight.

I've nowhere introduced the topic of accuracy. It has nothing to do
with your original query. Weight and mass can both be measured to
considerable accuracy. It all depends on method and standards.

And mass can be measured with much more accuracy than force can, but
that is entirely irrelevant to the point I was making.

Your claim was that the mass-measuring balances are, for a matter of
convenience, marked in units of force called pounds. I say that it is
in fact the other way around, that the cheap force-measuring spring
scales are marked in units of mass, which is indeed what we want to
measure. The kilograms used throughout the world, including most
hospitals in the U.S., for human body weight are indeed the proper SI
units for this quantity. The pounds used for this purpose are the
ones legally defined as 0.45359237 kg. Except, of course, for some
science teachers and some physics books written recently by authors so
miseducated (not uneducated, but actually mistaught) that they believe
pounds are not units of mass.

American Society for Testing and Materials, Standard for Metric
Practice, E 380-79, ASTM 1979.

3.4.1.2 Considerable confusion exists in the use
of the term weight as a quantity to mean either
force or mass. In commercial and everyday use,
the term weight nearly always means mass; thus,
when one speaks of a person's weight, the
quantity referred to is mass. . . .
Because of the dual use of the term weight as a
quantity, this term should be avoided in technical
practice except under circumstances in which its
meaning is completely clear. When the term is
used, it is important to know whether mass or
force is intended and to use SI units properly as
described in 3.4.1.1, by using kilograms for mass
or newtons for force.

This ASTM E 380 and a separate ANSI/IEEE Standard have now been
combined into a joint standard SI 10. I don't know if it says exactly
the same thing; but I am certain it doesn't say anything directly
contrary to this.

Of course, NIST also tells us the same thing. I'll get to that below.

A bathroom scale is not a balance. A balance has a scale (the marks
along which the balance weights are moved and the markings upon those
same weights).

However, you do ask for a reference and acknowledge the NIST as a
reputable source (many here ignore this commonplace):
http://physics.nist.gov/PhysRefData/...constants.html

There is absolutely nothing about pounds on this page. So don't be
bull****ting us.

That is the whole point. You don't see pounds there for mass do you?

I don't see pounds as units of mass because this page just lists units
in the International System of Units.

Exactly.

So why were you offering it as evidence that pounds are not units of
mass? Do you think I'm that stupid, that you can pull the wool over
my eyes so easily? Guess again.

Show me something from NIST saying that pounds are not units of mass.
Or from some textbook.

That's because pounds are not a unit of mass. They are a unit of
weight which is NOT a constant throughout the universe (nor on earth
for that matter).

Just your say-so? That's the best you can do?

I am a trained Metrologist. I have measured mass traceable to the
NIST. I have done this in four different Primary and Secondary
Standards Labs. I was the head Metrologist of two of them.

Wow! This is even better than I dreamed of. A genuine Capital-Letter
Metrologist. Of course, it's also pretty sad, as most people will
understand if they stick with me for the rest of this message.

I'm sure that as a Metrologist, you are well aware of one particular
subset of English units, used only in calculations, which is a
coherent, gravitational foot-pound-second system in which the derived
unit of mass is a slug, equal to 1 lbf·s²/ft. One of several such
subsystems, of course.

But if you are really a capital-letter Metrologist, and an old fart on
top of it (that system with the slugs was never used in physics
textbooks before 1940, and even a couple of decades later I learned
the system I'm about to describe first, before learning the one with
slugs--and you must be at least close to my age, and a genuine expert
on weights and measures on top of it all), you'll have a damn hard
time convincing me, or anyone else, that you are also not aware of a
much older coherent foot-pound-second system of mechanical units, the
absolute fps system in which the derived unit of force is the poundal,
the force which will accelerate the base unit of mass in this system
at a rate of one foot per second squared.

Now, fill in the blank, please: The BASE UNIT OF MASS in this oldest
English system of mechanical units is the _______________. Hint: it
is the "p" in this fps system.

BTW, while the gravitational fps system of units enjoyed a brief
heyday in science in North America, outside of North America the
absolute fps system with poundals remained the system of choice for
doing calculations in English units.

You probably also know that both of these limited use, coherent
systems of units are, like SI, coherent systems of units. That means
that in neither of these do we have any pints or gallons of any sort,
not U.S. liquid, not U.S. dry, and not imperial. Nor are there any
Btu, nor horsepower, in either system. Not only that, but there are
no ounces (neither avoirdupois nor troy, nor U.S. nor imperial fluid
ounces), no tons (neither long nor short, neither force nor mass), and
no miles or inches (and thus no pounds force per square inch either).

Of course none of our ordinary measurements are made in the context of
any of these specialized systems of mechanical units which serve as
calculation aids. The fact that many of the we use are not part of
these systems is one bit of evidence of that fact. That fact that
nobody ever measures (as opposed to calculating from other
measurements) mass in slugs is another. The fact that we can
generally choose any of several different systems of units to use in
our calculations, with no change in difficulty, is still another piece
in the puzzle.

Let's look at what the English physicists William Thomson (for whom
the SI unit of temperature is named) and Peter Guthrie Tate had to say
about this way back in 1879, Treatise on natural philosophy, 1879,
reprinted as Principles of mechanics and dynamics, quoted by Jim Carr
in Apr 1998 on newsgroups alt.sci.physics, sci.engr, sci.physics.

"By taking the gravity of a constant mass for the unit
of force it makes the unit of force greater in high than
in low latitudes. In reality, standards of weight are
masses, not forces. They are employed primarily in
commerce for the purpose of measuring out a definite
quantity of matter; not an amount of matter which
shall be attracted to the earth with a given force."

... description of merchant using spring scale to
defraud or be defrauded depending on latitude,
etc ... Jim Carr

"It is therefore very much simpler and better to take
the imperial pound ... as the unit of mass, and to
derive from it, according to Newton's definition
above, the unit of force."


Then you might also know what "weights" means in the English versions
of the international bodies charged with keeping our international
standards:

CGPM General Conference on Weights and Measures
CIPM International Committee for Weights and Measures
BIPM International Bureau of Weights and Measures

In the introduction to their SI brochure (available at
http://www.bipm.fr), the BIPM tells us for the first half-century of
their existence, their only responsibility was keeping the standards
for length and for mass. Take a wild guess which of those two
corresponds to "weights" in these names.

I can, OTOH, prove that pounds are indeed units of mass.

By a reference found at the NIST? I think you would have done that by
now if you could.

Cocky little *******, aren't you!

Just making clear that you accept the fact that doing so would prove
you wrong, before I do it.

I have already done so, of course, without referring to NIST, with
that description of the absolute fps system above.

But before we get to wandering around NIST's website, let's do a
little primary source research, and find the definition which NIST
considers controlling. For that we need to look to NIST's
predecessor, the National Bureau of Standards, and to the law of the
land.

Earlier in the 20th century, Congress had had the sense to delegate
the authority to make these definitions to the experts in the field
who know what they are doing, and had given the predecessor of NBS
this authority. This was officially implemented in 1959 by official
regulatory action by NBS, made official with its publication in the
Federal Register of 1 July 1959.

This redefinition of the pound was done in accordance with an
agreement reached among the national standards laboratories of several
of the most advanced nations in the world, not back in the Dark Ages
but in the middle of the 20th century, two years after Sputnik and the
year before the International System of Units was introduced. The old
U.S. definition, which had been a slightly different exact fraction of
a kilogram for the 66 years before then, was replaced by the new
international definition as 1 lb = 0.45359237 kg.

You can read the current U.S. law (this Federal Register Notice), as
well as a discussion of the earlier U.S. law and of the international
agreement, at one of these web sites (same document both places):
http://www.ngs.noaa.gov/PUBS_LIB/Fed...doc59-5442.pdf
http://gssp.wva.net/html.common/refine.pdf

Of course, the same definition is was also adopted in Canada, in the
U.K., in South Africa, in Australia, and in New Zealand, the other
parties to this international agreement. It is also used all around
the world, and was adopted by statute or regulation in some other
countries not a party to the original agreement, such as Ireland.

Now, let's get to the NIST web site. You obviously didn't follow the
links you provided to get to the right place. Start with the one you
recommended
http://physics.nist.gov/cuu/Units/units.html
click on Return to Units Home Page which takes you back up one level
to
http://physics.nist.gov/cuu/Units/index.html
click on Bibliography: Online publications and citations to go to
http://physics.nist.gov/cuu/Units/bibliography.html
Go down to NIST Special Publication 811 and first of all, order
yourself a free printed copy of this document. You need it. Then
look at it in the online version, either in .html or in .pdf,
whichever you prefer. I'll use the html version to give some links to
specific parts of it below; I also have the printed version, and I
have the .pdf version right on my computer.

I already know what you think of NIST. In another message, you told
us that "NIST describes all this at the links offered
and they do not equivocate nor banter terms casually. For any
Professional Engineer, they carry the force of law as the only
authoritative source for definition. "

This is NIST's official _Guide for the Use of the International System
of Units (SI)_, by Dr. Barry N. Taylor, reviewed and approved by both
the director of NIST and by his boss, the Secretary of Commerce. It
is cited as an authority not only by many of the national standards
agencies around the world, but also by the BIPM itself.

First, a word about Dr. Barry N. Taylor. He is not only a
professional metrologist with a Ph.D. in physics, but he has also
served on both the Consultative Committe on Units which advises the
CGPM (still on that, I think), and on the SUNAMCO Commission
(Commission on Symbols, Units, Nomenclature, Atomic Masses and
Fundamental Constants) of the International Union of Pure and Applied
Physics (IUPAP).

In other words, for the benefit of anyone else reading this, if
Richard Clark is a "Metrologist" then Dr. Barry Taylor must be a
"METROLOGIST" because even capitalizing all the letters won't
adequately show the difference between the two, especially when it
comes to expertise in the particular subfield related to teh
definitions of units of measure.

First, before we get to the pounds, let's digress a little bit and
finish up that loose end I left above.
http://physics.nist.gov/Pubs/SP811/sec08.html

Thus the SI unit of the quantity weight used in this
sense is the kilogram (kg) and the verb "to weigh" means
"to determine the mass of" or "to have a mass of".

Examples: the child's weight is 23 kg

The same is true for pounds, of course. Units of mass in this
context, as the term is used in physiology and medicine, and in
sports--the reasons we normally weigh ourselves.

There's more to the explanation in section 8.3, including a good
discussion of the force definition of weight often used in physics and
engineering. This section concludes with the excellent advice that

whenever the word 'weight' is used, it should be
made clear which meaning is intended.

Now, let's go to the extensive list of conversion factors found in
Appendix B to SP 811.
http://physics.nist.gov/Pubs/SP811/appenB8.html#P

To convert from to Multiply by

pound (avoirdupois) (lb) 23 kilogram (kg) 4.535 924 E-01
pound (troy or apothecary) (lb) kilogram (kg) 3.732 417 E-01

[The 23 is a reference to a footnote in the printed and pdf versions,
a note on a separate page in html]
http://physics.nist.gov/Pubs/SP811/footnotes.html#f23

23 The exact conversion factor is 4.535 923 7 E-01. All units
in Sec. B.8 and Sec. B.9 that contain the pound refer to
the avoirdupois pound.

This unit, of course, is not defined by this publication. This is
just the legal definition made by NBS in 1959.

Also, take a look at another section of American Society for Testing
and Materials, Standard for Metric Practice, E 380-79, ASTM 1979.

3.4.1.4 The use of the same name for units of force
and mass causes confusion. When the non-SI units
are used, a distinction should be made between
force and mass, for example, lbf to denote force in
gravimetric engineering units and lb for mass.

As you can see above, this sensible rule is also followed by NIST. It
is also followed by NPL, the U.K. national standards laboratory. It
is the older unit, the one more often used, and the one more likely to
be used by those who care least about the distinction, which gets to
use the original, unadorned symbol "lb"; it is the recent
*******ization, the less often used unit, and the one more likely to
be used by those who care most about the distinction, that must be
distinguished by using a different symbol, "lbf" instead.

That will prove that you are flat-out wrong in your claim that they
are not.

Well, I have seen a lot of math tossed over the transom here. But if
we are to work by your own standard, cite an NIST reference.

Just for practice, consider the troy system of weights. Unlike their
avoirdupois cousins, and unlike grams and kilograms, the troy units of
weight have never spawned units of force of the same name. They are
always units of mass; a troy ounce is exactly 31.1034768 grams, by
definition. There is not and never has been any troy pound force or
troy ounce force.


Hi Gene,

Sounds like you proved a pound is not mass.


No. You just proved that you are hopelessly ignorant when you get
outside your fields and start discussing things such as linguistics,
history, or the law.

The pages I offered provide a meaningful quote:
"The 3d CGPM (1901), in a declaration intended to end the
ambiguity in popular usage concerning the word "weight," confirmed
that:
The kilogram is the unit of mass..."

One of the most confusing and impossible to understand resolutions any
political body has ever passed. You will note that NIST places no
emphasis on this whatsoever.

Yes, even then there were evidently enough scientists so utterly
confused as to think that the standards they were keeping were
standards of force rather than the standards of mass which they always
had been. As were the old standards for pounds, naturally. Of
course, by that time, we in the United States has already abandoned
our independent standards for pounds, and we already defined them as
an exact fraction of a kilogram. So where does that lead you?

But of course, you are making a big mistake you think that this
particular resolution meant that we couldn't use kilograms force. In
fact, it was just the opposite--this very same resolution endorsed the
use of grams force and kilograms force by adopting a standard
acceleration of gravity, which is not a concept of physics but rather
of metrology, something which serves no purpose other than defining
units of force in terms of units of mass. Kilograms force had never
been well-defined units before then. Neither had pounds force, of
course--and what's more, even today pounds force don't have an
official definition. The de facto standard, never officially adopted
by any national or international standards agency, nor by any
professional organization, is probably to use the same standard
acceleration of gravity which is official for defining grams force and
pounds force, namely 980.665 cm/s² in the units used in that 1901
resolution, before mks systems had come into use, at a time when
neither slugs nor newtons had ever been used for the units they are
now.

Now go back to that Bibliography page on NIST and download NIST
Special Publication 330, which includes the unofficial English version
of this resolution, or at least the salient parts of it.
http://physics.nist.gov/cuu/Units/bibliography.html

Then pay special attention to the footnote added by NIST, found on
page 17 in the document's own pagination (I don't know the page number
in the pdf format):

[dagger] USA Editor's note: In the USA, ambiguity exists in
the use of the term weight as a quantity to mean either
force or mass. In science and technology this declaration
[CGPM (1901)] is usually followed, with the newton the
SI unit of force and thus weight. In commercial and
everyday use, weight is often used in the sense of mass
for which the SI unit is the kilogram.

Any other usage of "weight" in regard to the sensation of the action
of Gravity upon an amount of mass is outdated by more than a century
of understanding and convention.

You said weight is a force. This resolution clearly said that weight
is not a force, but merely something "in the nature of a force,"
whatever the hell that is supposed to mean.

But fortunately, in any case, nobody was ever damn fool enough to give
the 1901 CGPM any say-so on what "weight" means for the "net weight"
of my bag of sugar, or for the troy weight of a bar of gold or
platinum. That's outside their authority.

That resolution isn't seriously offered as proof of any change in
meaning of the word. In fact, I doubt that the 1901 CGPM ever
intended to change the meaning of the word--they wrongly thought that
they were merely stating existing definitions.

"Outdated by more than a century of understanding and convention"?
Nonsense. Go back and read that section 8.3 of NIST Special
Publication 811 again. That's 1995--hardly a century ago.

Need more. Here's 1989, in the still-effective official National
Standard of Canada, CAN/CSA-Z234.1-89 Canadian Metric
Practice Guide:

5.7.3 Considerable confusion exists in the use of
the term "weight." In commercial and everyday use,
the term "weight" nearly always means mass. In
science and technology, "weight" has primarily
meant a force due to gravity. In scientific and
technical work, the term "weight" should be
replaced by the term "mass" or "force," depending
on the application.

5.7.4 The use of the verb "to weigh" meaning "to
determine the mass of," e.g., "I weighed this
object and determined its mass to be 5 kg,"
is correct.

Note that "nearly always" is much stronger than "primarily"; they even
got that part right. Note further the difference usage for the noun
forms in 5.7.3 and the verb forms in 5.7.4; for the former, the
meaning is context-specific, but for the latter that definition is
unqualifiedly called "correct" (which does not, of course, say
anything one way or the other about the use of the verb to mean to
determine the force due to gravity, which is also correct).

Need more. Here's 2003, on the web pages on the National Physical
Laboratory (NPL), the official national standards agency of the United
Kingdom of Great Britain and Northern Ireland:

NPL FAQ
http://www.npl.co.uk/force/faqs/forcemassdiffs.html

Weight
In the trading of goods, weight is taken to mean the
same as mass, and is measured in kilograms. Scientifically
however, it is normal to state that the weight of a body is
the gravitational force acting on it and hence it should be
measured in newtons, and this force depends on the local
acceleration due to gravity. To add to the confusion, a
weight (or weightpiece) is a calibrated mass normally
made from a dense metal, and weighing is generally
defined as a process for determining the mass of an
object.

So, unfortunately, weight has three meanings and care
should always be taken to appreciate which one is
meant in a particular context.

Note that they are talking about DIFFERENT MEANINGS of the word
"weight." Just as NIST does. Just as ASTM does. Just as the
Canadian Standard for Metric Practice does. Just as any good
dictionary does.

That, of course, is how the word weight entered the English language
over 1000 years ago, meaning the quantity measured with a balance. A
quantity which you yourself explained so lucidly to be mass, not the
force due to gravity. Of course, when those tribesmen in what is now
England were looking for a word to use to measure how much stuff they
have, when they buy and sell goods, they didn't make any mistake when
they invented this word "weight" for that purpose, did they? They
couldn't have used "mass" for this quantity instead, unless they had
happened to choose those phonemes for the word they invented. Mass
didn't have this meaning until more than 750 years later, when some
obscure translator translated Newton's major work into English after
Newton's death. Or do you think it was a mistake that these heathens
didn't figure out the God-given word they were supposed to invent for
this purpose?

There is no error when we use the very same word, with the very same
meaning, for the very same purposes today. We have a prior claim to
this word by 3/4 of a millennium over the physicists who recently
borrowed it and often use it with a somewhat different meaning.
Sometimes we borrow the physicists meaning, sometimes we use the
original meaning. But like all the experts tell you, because of these
ambiguities, you should just avoid using the term "weight" in a
technical context--and if you do use it, make damn sure your meaning
is clear.

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/
Gentlemen of the jury, Chicolini here may look like an idiot,
and sound like an idiot, but don't let that fool you: He
really is an idiot.
Groucho Marx

On Thu, 25 Sep 2003 03:41:10 GMT, Gene Nygaard
wrote:
Do you think I'm that stupid, that you can pull the wool over
my eyes so easily?

Hi Gene,

As I pointed out earlier, your feelings belong at the end of the line
with the rest whose minds I cannot change.

73's
Richard Clark, KB7QHC

Gene Nygaard wrote:

Apparently you are claiming that pounds are not units of mass.

Where did you learn that?

Being the skeptic that I am, how can I convince myself that that is
true? Is there some textbook, or something from some national
standards agency, that would help me verify this?

Gene Nygaard

Nice web page you have on the subject, but I suspect it is not
quite so cut and dried as you make out.

I have a strong recollection (from many years ago) of being
taught that pounds where force. Going to google with 'pound
mass force' yields some modern university teaching material
which says the same. My ancient thermo text uses lbf and lbm
throughout to eliminate confusion.

There seems to be little doubt that today the pound is
defined in terms of the kilogram so is clearly a unit of
mass.

But usage of the pound seems to be less consistent. Consider
pounds per square inch or foot-pounds; in each of these
the pound is a unit of force.

I expect the definition of pound will be argued for some
years to come.

Let's just all go metric. The only really confusing measure
there seems to be the definition of the litre.

....Keith

Gene, thanks for the compliment in calling the Program Chief Engineer
of the USAF MX [Peacekeeper] Re-Entry System/Re-Entry Vehicle a fool.

It says a lot about you. I forgive you.

Dave, W1MCE
+ + +

Gene Nygaard wrote:
not concerned enough about the possibility that fools like you

On Thu, 25 Sep 2003 06:45:29 -0400, wrote:

Gene Nygaard wrote:

Apparently you are claiming that pounds are not units of mass.

Where did you learn that?

Being the skeptic that I am, how can I convince myself that that is
true? Is there some textbook, or something from some national
standards agency, that would help me verify this?

Gene Nygaard

Nice web page you have on the subject, but I suspect it is not
quite so cut and dried as you make out.

It is. I never claimed that pounds force aren't used also.

I have a strong recollection (from many years ago) of being
taught that pounds where force. Going to google with 'pound
mass force' yields some modern university teaching material
which says the same. My ancient thermo text uses lbf and lbm
throughout to eliminate confusion.

But that isn't what our resident Capital-M Metrologist was telling us.
He claimed flatout that pounds are not units of mass.

Furthermore, he also set the ground rules that I could prove him wrong
from the NIST web pages. Yet even though I have indeed done not only
that, and with a dozen other reasons and citations as well, he remains
recalcitrant in his erroneous ways.

Richard Clark is a big windbag, of no substance whatsoever. But much
worse than that is the fact that he has absolutely no integrity.

Yes, some do use lbm and lbf. Or some other variation. I remember
one textbook using p for pounds force and lb for pounds mass.

Here's the way the British physicist who named the slug put in, in the
little treatise in which he introduced this unit to the world:

In the interests of clear teaching, the convention
(which I am glad to see has been adopted in America)
has been adhered to throughout, of using the word
‘pound' when a force is meant, and ‘lb.' when a mass
is meant, and I have ventured to give the name of a
‘slug to the British Engineer's Unit of Mass, i.e. to the
mass in which an acceleration of one foot-per-sec.-
per-sec. is produced by a force of one pound.

It's easy to see why that convention didn't go very far. People would
naturally like to have both a spelled out word and a symbol for both
pounds. He also says, another source showing that Richard Clark is an
incompetent metrologist (and if is also a professional engineer,
guilty of malpractice by his own words because he doesn't follow
NIST's definitions):

British Absolute Unit of Torque. Since in the British
absolute system, in which the lb. is chosen as the unit
of mass, the foot as unit of length, and the second as
unit of time, the unit of force is the poundal, it is
reasonable and is agreed that the British absolute
unit of torque shall be that of a poundal acting at a
distance of 1 foot, or (what is the same thing, as regards
turning) a couple of which the force is one poundal and
the arm one foot. This we shall call a poundal-foot,
thereby distinguishing it from the foot-poundal, which
is the British absolute unit of work.

A.M. Worthington, Dynamics of Rotation: An Elementary Introduction of
Rigid Dynamics, London, New York, Bombay, Calcutta, and Madras:
Longmans, Green, and Co., 1920

As I pointed out to Richard Clark, however, according to the modern
rules, it is the pound force which must be distinguished from pounds
in their original and still most common meaning as units of mass. The
ones using pounds mass (the unit much more often used by those who
care least about the distinction--witness the thousands of items in
every grocery store and hardware store in America measured in pounds)
are the ones who can get away with using the original "lb" symbol.

There seems to be little doubt that today the pound is
defined in terms of the kilogram so is clearly a unit of
mass.

I can't understand how so many science teachers, and even textbook
authors in the past decade or so, can remain oblivious to this simple
fact.

But usage of the pound seems to be less consistent. Consider
pounds per square inch or foot-pounds; in each of these
the pound is a unit of force.

Yes, and for all those items in our stores, the pound is a unit of
mass. For density in pounds per cubic foot or pounds per gallon or
pounds per cubic yard (civil engineers) or pounds per cubic inch
(mechanical engineers), pounds are units of mass. For defining a
British thermal unit, how much water? Certainly not an amount that
exerts a certain amount of force. By the same token, the pounds in
the denominator are units of mass if you say the latent heat of fusion
of water is 80 Btu/lb, or if you express specific heat capacity in
units of Btu/(lb·°F).

Of course, we also have kilograms as units of force when you see the
thrust of jet or rocket engines expressed in kilograms, or pressure
gauges in kg/cm², or torque wrenches in "meter kilograms" rather than
newton meters (still readily available; I have one). The only
difference is that these uses are decreasing. That's because the
metric system is still fully supported and updated, and kilograms
force are not part of its modern version, the International System of
Units (SI). The English units, OTOH, are like obsolete versions of
software--still often usable for the purposes the user wants, but
eventually you may have to upgrade if you want to communicate with the
rest of the world. Nobody is ever going to bother to tell us to stop
using pounds force, without telling us to stop using pounds as units
of mass as well.

I expect the definition of pound will be argued for some
years to come.

Let's just all go metric. The only really confusing measure
there seems to be the definition of the litre.

The litre, of course, is not part of SI. While its definition was
confusing around the time I first learned this, when it was different
from a cubic decimeter, that changed in 1964 when the CGPM redefined
it, restoring the definition as exactly 1 dm^3, and said that under
that definition it would be acceptable for use with SI, something that
hadn't been true for the first four years of the existence of SI.

No. You have the mole, which shares its name with the pound mole and
the kilogram mole, both still used. Guess nobody has the political
will to rename it the loschmitt.

For other non-SI units, of course, the calorie is the absolute worse,
with several different flavors in each of two major groupings,
differing from each other by a factor of a thousand.

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/

On Thu, 25 Sep 2003 12:13:47 GMT, Dave Shrader
wrote:

Gene, thanks for the compliment in calling the Program Chief Engineer
of the USAF MX [Peacekeeper] Re-Entry System/Re-Entry Vehicle a fool.

It says a lot about you. I forgive you.

Gee, if I'd known you were so important, I'd really have taken you to
task for being too damn stupid to understand what you read in Sears
and Zemansky!

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/

On Thu, 25 Sep 2003 12:13:47 GMT, Dave Shrader
wrote:

Gene, thanks for the compliment in calling the Program Chief Engineer
of the USAF MX [Peacekeeper] Re-Entry System/Re-Entry Vehicle a fool.

It says a lot about you. I forgive you.

Dave, W1MCE
+ + +

Gene Nygaard wrote:
not concerned enough about the possibility that fools like you

Since you aren't honest enough to tell us exactly what Sears and
Zemansky said in 1956, I'll tell everyone what they said in 1970. If
there are any significant differences, feel free to point them out.
This thing is, I know that Sears and Zemansky weren't going to lie
about this, because they grew up using poundals, which are by
definition the force which will accelerate a MASS of 1 lb at a rate of
1 ft/s².

Francis Weston Sears and Mark W. Zemansky, University Physics,
Addison-Wesley, 4th ed., 1970.

[page 3]

1 pound mass = 1 lbm = 0.45359237 kg

[The actual number will, of course, be different in 1956, because the
U.S. didn't adopt this definition until 1959 (it had been in use in
Canada since 1953, six years before the international
redefinition).--GAN]

[page 4]

We select as a standard body the standard pound,
defined in section 1-2 as a certain fraction
(approximately 0.454) of a standard kilogram.

[page 59]

In setting up the mks and cgs systems, we first selected
units of mass and acceleration, and defined the unit of
force in terms of these. In the British engineering system,
we first select a unit of force (1 lb) and a unit of
acceleration (1 ft s^-2) and then define the unit of mass as
the mass of a body whose acceleration is 1 ft s^-2 when
the resultant force on the body is 1 lb.

end quote

Now, Sears and Zemansky might be incompetent for not allowing for the
fact that there are going to be people out there who are too blamed
stupid to understand that that adjectival phrase "British engineering"
has some meaning, and that it identifies one particular limited subset
of the British units. It's perhaps even understandable, because that
fact would be quite clear to anyone who, like them, had grown up using
poundals in a "British absolute" system of units.

However, that doesn't change the fact that you are in fact one of the
people who are that stupid.

--
Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/
"It's not the things you don't know
what gets you into trouble.

"It's the things you do know
that just ain't so."
Will Rogers

On Thu, 25 Sep 2003 12:13:47 GMT, Dave Shrader
wrote:

Gene, thanks for the compliment in calling the Program Chief Engineer
of the USAF MX [Peacekeeper] Re-Entry System/Re-Entry Vehicle a fool.

Is that as good as being chief of the Mars Climate Orbiter program as
evidence of competence in the use of units of measure?

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/

On Thu, 25 Sep 2003 06:45:29 -0400, wrote:

Let's just all go metric. The only really confusing measure
there seems to be the definition of the litre.

...Keith

Hi Keith,

You mean liter? ;-)

73's
Richard Clark, KB7QHC