On Fri, 26 Sep 2003 15:44:09 -0700, Jim Kelley
wrote:
Gene Nygaard wrote:
Now, perhaps you think something changed between 1960 and 1981 when
the revised Halliday & Resnick came out.
Hi Gene,
You'll be surprised to learn that a lot has changed since 1960.
Show me some justification for
a change, some change in facts, that would justify a different "point
of view" as you put it.
Since it's apparent that you have no need to change your point of view,
I find that I likewise have no need to change your point of view.
Why do you think torque wrenches have the unit 'foot-pounds' printed on
them if the pound is a unit of mass?
Mine also has "meter kilograms" on it. What does that tell you?
Note that I've said all along that pounds force exist as well. I've
just been attacking the idiots who claim that pounds are never units
of mass.
2. Who declared whatever the standard is to be the standard?
I don't know, but I guess they should have spoken to you about it
first. ;-)
Did anybody do so?
Missed that part, didn't you!
4. To whom does the standard apply?
It applies to everyone except the people who apparently don't want it to
apply to them. :-)
6. What is the exact relationship between pounds force and the metric
units, or the relationship to the greatest precision in which it can
be expressed if it is not exact?
It's not like it's a big secret or anything.
7. Even if all this were true, would it mean that the pound is a unit
of mass?
The pound is generally accepted to be a unit of force. Otherewise,
they'd have to get rid of all the PSI pressure gauges.
And what about Btu's? Specific heat capacities in Btu/(lb °F)?
Is there some rule that says that textbook authors are
allowed to bury their heads in the sand, and ignore the real world
which does in fact use the definition agreed on by those six national
standards laboratories of some of the most advanced nations in the
world in 1959?
It really wouldn't hurt you to pick up a (modern) physics book and just
look at it some time. Or maybe you're of the opinion that all modern
physics books are wrong?
But here's a question: if one pound of mass weighs one pound and exerts
one pound of force, given F = MA,
There's your error, a faulty premise.
All we really know is that force is proportional to mass times
acceleration. One way we can express this is F = k·m·a. Yes, we can
choose our units so that the proportionality constant is one, but we
don't have to do so. In any case, the k, whether it is 1 or some
other number, is always the same for a particular choice of units for
those three quantities.
Also, when we do choose our units that way, we have several different
ways we can do so using English units, as well as several ways we can
do so using metric units (only one of which is SI, the modern metric
system).
what are the units of A (little g)?
Or, would you claim one pound of mass actually weighs 32.17 pounds?
A pound of mass at sea level on Earth exerts a force of 32.088
poundals and 32.258 poundals (not pounds force). It will exert a
force of something like 32.024 poundals atop Mt. Chimborazo, the
highest mountain on Earth (at least in both ways relevant to this
example). It exerts a force of somewhere between 0.9973 lbf and
1.0026 lbf at sea level.
--
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