On Thu, 2 Oct 2003 15:24:23 -0500 (CDT),
(Richard Harrison) wrote:

Gene Nygaard wrote:
"Why are you still refusing to deal with the "meter kilograms" on my
torque wrench---?"

Multiply the meters by 3.28 and multiply the kilograms by 2.2, and you
will have torque in their product computed in foot pounds. Or, just
multiply the dial reading by 7.22 for ft.lbs. Torque is the product of
force and distance.

It's no surprise that you don't have any problem with this. Don't you
remember when I told you that your views were at odds with those of
Jim Kelley (and half a dozen others in this thread as well)?

It's Jim Kelley who is having great difficulty dealing with these
"meter kilograms." Their existence demolishes one of his major
arguments. Will he, or any of the others making similar foolish
arguments, ever address this?

I don't think it's that you understand all this a whole lot better
than those others. Rather, you are more like those rocket scientists
who blissfully get specific impulse in "seconds" by using pounds mass
to cancel out pounds force. In SI, the units of specific impulse are
N·s/kg, or the equivalent m/s.

Weight is a force produced by gravity on a particular mass.

One definition of weight, yes.

The indication on a torque wrench is muscle force times lever length. It
directly has little relation to gravity in most torque wrench
applications.

I don't understand why you think that's even something worth bothering
to point out. Do you think this would have some bearing on the fact
that both Jim and I have characterized torque as "force times
distance"? How? The word "weight" didn't enter into those
discussions of torque, as far as I can remember.

Or are you just pointing out the unrelated (at least in the sense that
it wasn't part of our discussion of torque) fact that pounds force are
often used for things that are never called "weight," so identifying
them as "units of weight" is pretty stupid? At least, compared to the
identification of pounds mass as "units of weight" since in the
definition of weight as a synonym for the "mass" of physics jargon,
that's what mass units such as troy ounces or avoirdupois pounds or
kilograms are always used for--something that can be called "weight"?

Weight is the easy way to determine mass. Computing mass from collection
of acceleration data would be more complicated. M = F/A

Principle of equivalence. Look that up.

OTOH, computing force due to gravity with a balance is not merely
"more complicated," it is impossible without additional information
you don't get from the process of weighing it with the balance.

For example, suppose I have a bar of gold that weighs 401.23 troy
ounces on my balance. How much force does it exert due to gravity, at
my location on Earth? Use any force units you choose--poundals,
newtons, kilograms force, sthenes, whatever--just remember that troy
ounces are not units of force.

Now suppose I take the whole works to the middle of the Sea of
Tranquillity on the Moon, and weigh it again. It weighs 401.25 troy
ounces. How much force is it exerting due to gravity now? Once
again, any units of force will be fine.

Now, I'm also sure that you are well aware that we call what we
measure with a balance "weight," aren't you? Can you tell me why so
many science textbook authors appear to be unaware of this commonly
known fact? (They aren't really, it is a sham in most cases, and
others try to weasel out of it by imagining some "error" is that
usage.) Would you suppose that this might have something to do with
the great emphasis some of them place on the operation of a spring
scale, going into great detail about how they work, while ignoring the
only weighing devices anybody had ever used for the 7000 years or so
that people had been weighing things, before those spring scales first
appeared in the 19th century?

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