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When I google, I get a definition for density, which is what I figured would happened. Unless I am mistakenabout something, saying mass density is a waste of breathe and misleading.
"Density: There are two kinds of density, "weight density"
and "mass density". We will only use mass density and when we say:
"density", we will mean "mass density". Density is mass per
volume. Lead is dense, Styrofoam is not. The metric system was
designed so that water will have a density of one gram per cubic
centimeter or 1000 kilograms per cubic meter. Lead is about 10 times
as dense as water and Styrofoam is about one tenth as dense as water."
What really chaffes me is the Pro/E use of weight/volume and calling it density in it's "default" unit system...
Even worse we had an intern in here (BSME student), giving his semester end presentation, that couldn't figure out why the FEA Sr. Engineer was having him report density in (lbf-sec)/in^3 for materials they were doing comparison studies on. He couldn't figure out what was going on and why he had to keep dividing "density (lb/in^3)" by 386.4 to get it into (lbf-sec/in^3) = blobs/in^3
Well said intern has not had a dynamics of machinery class yet, so he'll get it eventually.
You should be VERY careful about how you use, and expect others to provide, this type of data. When asking for it, you must be very specific and include the term "mass" or "weight". Different disciplines dealing with solid mechanics or dynamics use either form, and they clearly are different. Just because we can find somebody's definition of the term "density" to default to the specific "mass density" quantity doesn't mean "mass density" does not exist. I see both used in my industry, so we need to be careful. There is such a thing as "mass density" and in a forum like this one, we should specify which it is we
Okay, so what is the mass density and for that matter what is weight density?
The only difference between mass and weight is gravity. So, are you saying the only difference between mass density and weight density is... gravity?If we are just mulitipling by other "items", then I have a new one... speed of light density. How ya like them apples!
Sorry, if you saw my first post,had to edit... gravity is not a constant.
What really chaffes me is the Pro/E use of weight/volume and calling it density in it's "default" unit system...
Even worse we had an intern in here (BSME student), giving his semester end presentation, that couldn't figure out why the FEA Sr. Engineer was having him report density in (lbf-sec)/in^3 for materials they were doing comparison studies on. He couldn't figure out what was going on and why he had to keep dividing "density (lb/in^3)" by 386.4 to get it into (lbf-sec/in^3) = blobs/in^3
Well said intern has not had a dynamics of machinery class yet, so he'll get it eventually.
This topic came about in a similiar way. An "extended" co-worker said he had spent time trying to figure out the difference between density and mass density. I replied "nuttin". He said well Pro/E uses mass density. In his defense, he thought the difference was similiar to that of volume and specific volume. But he wasted time all the same.
You are thinking of the word density as a specific term. We tend to get lazy and use the word by itself.
Consider population density,
current density,
prime number density,
or the density of stars in a galaxy.
None of these have anything to do with mass over volume, or weight over volume.
Engineers must distinguish between mass and weight. It is usually best to use mass density as opposed to weight density. Distinguishing which one we are using will save us from ourselves. It would be nice if weight density were eliminated from use.
1) Mass is a measurement of the amount of matter something contains,
while Weight is the measurement of the pull of gravity on an object.
2) Mass is measured by using a balance comparing a known amount of
matter to an unknown amount of matter. Weight is measured on a scale.
3) The Mass of an object doesn't change when an object's location changes. Weight, on the otherhand does change with location.
end quote.
My weight density on the moon would be about 28 lbs/ft^3.
My MASS density would be the same on earth as it is on the moon.
My mass density is 170/32.2 lbf = (approx) 5.27 lbf/ft^3
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