lbmass

[cadman777]

someone please clarify something for me:
i'm using aip2009
the physical properties tab has the a.s. MASS units as 'lbmass'
why is it called 'mass' when it is actually WEIGHT?
this is how i understand the units related to this:
a of g = 32.2 ft/sec^2
slug = avd. lb (with no a. of gravity)
lb = a of gravity x slug
lbmass = 1/32.2 x slug
if this is right, then why does inventor call lbmass = WEIGHT?
are they re-defining the international standard in their own terms?
also, on the physical properties tab, what exactly does AREA define?
does it take the sum total of EXTERNAL surfaces of an assembly, while disregarding the INTERNAL surfaces of hollow bodies?
... chris

[JDMather]

Q2 Suppress shell and check iProperties for Area.
Unsupress shell and check iProperties for Area.

Oops, just realized you referred to assembly area.
Place two instances in assembly and repeat above experiment.
Edited by: JDMather on Aug 12, 2009 9:29 AM

[cadman777]

thanks jd ... chris

[msklein]

you caused me to have to think, bad idea this early in the morning, just getting my first cup of coffee.
The National Institute of Standards and Technology generally defines them as the same, but if you dig a little deeper they get the technical definitions out, weight has to do with the gravity of the object. Mass of an object is a measure of the object's inertial property. So as i read it Adesk is correct in how they have defined it in the proprieties list. no let me go back to sleep tell i finish my second cup.
msk

[cadman777]

msk, thanks.
i went to nist and didn't find what i was looking for.
it was a shit load of bureaucratic data, not origanized in a manner that was easy to find what i wanted
it's not that i don't believe you, but i want to see POUND, SLUG, & POUND-MASS defined side-by side from an official source. wiki is not an official source for me, but only serves as a guideline or starting point.
cheers ... chris

[msklein]

don't use WIKI for anything other than a general begriming ref for help to look else where, too many wako's putting info in!!!!!! gov't standards, what do you expect that's why i used the term in general. I didn't think or mean to create a link to WIKI, i listed the gov't dept for research info.
msk

[cadman777]

msk,
i agree
do you have web link that has a nice clear statement of the units that we're discussing?
cheers ... chris

[BKoomler]

If the specific units are an issue change them in the document settings. I also found an explination in Machinery's Handbook 26th edition page 114.

[msklein]

didn't look into it that far.
msk

[BKoomler]

I already had it open in front of me.

[petercharles]

While trained in foot - pounds - seconds, there are merits in metre - kilogramme - seconds. Not least of which is mass is kilogramme and force is Newtons so you don't get hung up with pounds force and pounds mass!

[cadman777]

bk, thanks
i have and read the mach hb #26 p114 earlier, but didn't see lb-mass in it
they call the slug a pound/g and it's a crazy way to say it
anyways, thanks for the tip on changing the settings
my main concern is to figure out exactly what inventor means by 'lbmass'
it tests out to be pounds
but i learned lbmass to be 1/32.2 slugs
question still not answered
although i'm accustomed to imperial system units, i can see the value in metric
it's WAY easier to use when doing calcs

[msklein]

don't know where you are located, but at a lot of the companies i've worked for just saying that would get you fired. I wish we would get over it and join the rest of the world. Maybe before i die, but then i would not hold my breath on it. Spent many years in that unamed high tech capitial, you would think they would be open to it.
msk

[petercharles]

In the UK where the greatest improvement in engineering productivity came with "units of ten" and being able to combine metrication (10mm in a cm, 100 cm in a m, 1000 gm in a kg, 1000 kg in a tonne) with the new electronic calculators. Out went slide rules and the famous "Inskips Combined Tables" and in came fast and accurate calculations.