Wow!

In SI: force is in Newtons
mass is in kg
distance is in meters
time is in seconds - and answers are always in SI units if
you use SI units.

A mass in a gravitational field has a force associated. That force is
not a mass even if it is (some of the time) proportional to mass.

When certain kinds of engineers provide me with specifications
involving pounds I shudder. Each use is converted into its equivalent
in SI. The context helps. An assumption of the strength of the
gravitational field needs to be used. Then I evaluate their work using
SI (and the same assumption about the gravitational field). In SI,
force and mass are quite distinct.
I continue to be amazed by the awesome ability of some engineers to
use a single term for two entirely different things. Use SI and the
answers are SI.
73 Mac N8TT

--
J. Mc Laughlin - Michigan USA
Home:

"J. McLaughlin" wrote:
When certain kinds of engineers provide me with specifications
involving pounds I shudder. Each use is converted into its equivalent
in SI. The context helps. An assumption of the strength of the
gravitational field needs to be used. Then I evaluate their work using
SI (and the same assumption about the gravitational field). In SI,
force and mass are quite distinct.
I continue to be amazed by the awesome ability of some engineers to
use a single term for two entirely different things. Use SI and the
answers are SI.

This captures the essence of the issue. The question is not so much
'are pounds mass or force?', but, rather, 'what did the author
mean when writing pounds?'

An engineer who believes that pounds are always mass will make
just as many errors as one who believes pounds are always force.

....Keith

On Thu, 25 Sep 2003 12:02:12 -0700, Jim Kelley
wrote:



Gene Nygaard wrote:
Up there in the Great White North, they use those dinky little
"litres" where it takes 4.54609 of them to make a gallon, rather than
the man-sized liters we have, which only take 3.785411784 to make a
gallon. ;-)

I suspect it's not the litre which is different, but the gallon which is
different. The British Imperial Gallon occupies 277.4 in^3, while the
gallon you're thinking of occupies 231 in^3.

Oh, good grief. Don't tell me the Canucks use different cubic inches
too, and don't even distinguish them with the spelling like they do
for "litres" vs. "liters"!

Are you ready for your next assignment, Sherlock? I'm wondering if
you'd be willing to take on another job for me. Do you suppose you
could help me track down a missing wink? Apparently there was one
that didn't show up on your newsreader--they look something like
this-- ;-)

What's your opinion of converting US speedometers from miles/hr to
furlongs/fortnight?

I think you'd be one of those guys who try to talk the talk, without
having learned how to walk the walk. You've never actually calculated
any speeds in furlongs per fortnight yourself, have you?

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

On Thu, 25 Sep 2003 23:28:25 -0400, "J. McLaughlin"
wrote:

Wow!

In SI: force is in Newtons
mass is in kg
distance is in meters
time is in seconds - and answers are always in SI units if
you use SI units.

A mass in a gravitational field has a force associated. That force is
not a mass even if it is (some of the time) proportional to mass.

When certain kinds of engineers provide me with specifications
involving pounds I shudder. Each use is converted into its equivalent
in SI. The context helps. An assumption of the strength of the
gravitational field needs to be used. Then I evaluate their work using
SI (and the same assumption about the gravitational field). In SI,
force and mass are quite distinct.
I continue to be amazed by the awesome ability of some engineers to
use a single term for two entirely different things.

It helps to be too stupid to know that there are in fact two entirely
different things. There are several of those people in this thread.

Not for the accuracy of the result, of course. But you can blithely
plug in the numbers and get an answer of some sort.

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

"Gene Nygaard" wrote in message
...

Are you ready for your next assignment, Sherlock? I'm wondering if
you'd be willing to take on another job for me. Do you suppose you
could help me track down a missing wink? Apparently there was one
that didn't show up on your newsreader--they look something like
this-- ;-)

Well, Gene. One never knows. I appologize. Your bit about the pound was
funny too, but didn't have the smiley face. Next you'll be telling us it's
a unit of currency! :-)

What's your opinion of converting US speedometers from miles/hr to
furlongs/fortnight?

I think you'd be one of those guys who try to talk the talk, without
having learned how to walk the walk. You've never actually calculated
any speeds in furlongs per fortnight yourself, have you?

A grad student an I made an overlay for his speedometer - must have been
close to 15 years ago now.

73, Jim AC6XG

wrote:
An engineer who believes that pounds are always mass will make
just as many errors as one who believes pounds are always force.

...Keith

Yep. And an engineer who uses pounds for either will either make or
cause more mistakes than one who doesn't. Remember the Mars Climate
Orbiter?

73, Jim AC6XG

Gene Nygaard wrote:
Apparently Halliday and Resnick were a lot smarter a couple of decades
earlier, when they were only a little past their prime:

Hey Gene,

Maybe Halliday and Resnick in fact _avoided_ becoming "past their prime"
when they adapted their point of view to the one which now prevails.

73, Jim AC6XG

On Thu, 25 Sep 2003 07:14:09 GMT, Richard Clark
wrote:

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.

I proved you wrong, from the NIST site--your groundrules--and from
many other sources as well. I gave you a web page from NIST defining
the pound as a unit of mass exactly equal to 0.45359237 kg.

Now I have a challenge for you, Mr. Metrologist:

Show me an official definition of a pound force on the NIST pages.
Bet you can't do so. Note that a conditional definition, with a big
"if", indicating that this is only one possible acceptable definition,
is not sufficient--I want an official definition.

If you can't do that, try a broader problem: Show me an official
definition of a pound as a unit of force from ANY law of ANY country
in the world, or from ANY standard of ANY national or international
standards organization, or from ANY standard of ANY professional
organization.

Are you up to the challenge?

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

On Fri, 26 Sep 2003 18:21:49 GMT, Gene Nygaard
wrote:
Now I have a challenge for you, Mr. Metrologist:

Hi Gene,

What are your credentials? Can one expect you have at least a degree
in English? ;-)

If not, you will have to assemble at the end of the line with the
rest. Please leave room in front of you for those with serious
differences who might arrive later (almost guaranteed).

73's
Richard Clark, KB7QHC

On Fri, 26 Sep 2003 19:18:23 GMT, Richard Clark
wrote:

On Fri, 26 Sep 2003 18:21:49 GMT, Gene Nygaard
wrote:
Now I have a challenge for you, Mr. Metrologist:

Hi Gene,

What are your credentials? Can one expect you have at least a degree
in English? ;-)

My credentials won't change what you WON'T find on the NIST web pages,
wimp!

Show me the official definition of a pound as a unit of force from
NIST, either on their web pages or from any published document of NIST
or its predecessors.

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