Gene Nygaard wrote in message . ..
On 11 Dec 2003 09:52:27 -0800, (Fred the Red
Shirt) wrote:

Gene Nygaard wrote in message . ..
On 10 Dec 2003 06:50:50 -0800, (Fred the Red
Shirt) wrote:



I was merely pointing out that you have it ass-backwards. There is
absolutely no looseness in the use of pounds as units of mass.

Non-sequitor. Loosness was never at issue.

It was after you brought it up, saying: "Ambiguity exists because it
is popular in some disciplines to use a unit of mass defined (loosely)
as that mass which weighs one pound."

Which is entirely true.


In actual fact, pounds are defined very specifically as 0.45359237 kg
exactly.

Which I'll also assume is entirely true (Unless we want to
quibble as to the distinction between dfining a unit of measure
and determining the standard value for that unit, which will
turn on how one defines 'definition'.)

But I would hardly call that a loose definition. If you prefer,
I can elaborate on teh meaning of loose defintion by pointing out
that loosely speaking, pounds mass and pounds force may be circularly
defined.

The pound mass is a mass with a weight of one pound and the pound
force is weight of a one pound mass within the context of weight as
force. We could quibble about where you measure the gravitational
acceleration but then we wouldn't be defining things loosely, would
we.

Now, to establish a standard value for either unit one can use,
a more formal version of at most only one of those defintions.

You don't get there by starting with a pound force. You can
use that definition, in conjunction with some value for a standard
acceleration of gravity (and none has ever been officially adopted for
this purpose, so there are a few different values which are used for
this), to define a pound force.

I think you are confusing definition with standardization. One
can define one thing in terms of anther and vice-versa without
need to state any way to determine a standard value for either.


If your confusion about this were an isolated problem suffered by you
individually, it would hardly be worth comment.

There was no confusion on my part.

You, OTOH, are confabulating defintion, standardization, jargon,
ligusitics, law, pedantry and god knows what else for no apparent
purpose.


But the fact of the
matter is that this confusion is also shared by several authors of
physics textbooks, and many science teachers at various levels. You
could easily find textbooks and web sites making the same claims that
you made, many not merely implying but specifically stating that
pounds mass are a substandard derivative of the pound as a unit of
force--there is in fact widespread, systematic miseducation on this
point.

I have found pounds mass to be a poor choice of units for purposes
of most calculations. I prefer to use the slug which is unambiguously
a unit of mass.

If one works first with pounds force, later with pounds mass, then one
is introduced to pounds mass as deriviative of pounds force. Again,
it matters not how the MBS determines the standard value for either.


Slugs, OTOH, are only defined as units of mass. No ambiguity there.

The OP referred to slugs as ambiguous. The OP had it bass akwards.

No. Russell Kent originally claimed that pounds ARE NOT units of
mass. As he did so, he claimed that slugs are the English units of
mass.

I'm not going to check to see if he wrote that or not since that is
not what caught my eye. I'll confirm that he wrote this:

In
http://groups.google.com/groups?hl=e...0ti.com&rnum=4
Russel Kent wrote:

I was taught (perhaps incorrectly) that the unambiguous term for
weight
(scientific meaning) in the English system was "slugs".

...
But he never called slugs ambiguous nor implied that slugs are
ambiguous.

Ok, he referred to slugs as the unambiguos term (not unit) for (not
of)
weight. Which not possible given that weight itself is an ambiguous
term, though not in phyusics in which weight it usually defined by
Newtons law of gravitational attraction.

But you seem to think that it is incorrect to loosely define a thing
if that definition does not strictly follow in a linear fashion, from
a published standard.

If one only defines things in a manner that strictly follows in a
linear fashion from a published standard how could one ever define
a thing 'loosely?'

--

FF