Is there any context in which "weight density" would actually be used in real life?

[AngieW in Texas]

The only place I have ever seen the term "weight density" used is in Hewitt's Conceptual Physics. I was pretty shocked when he went on and on and on about centrifugal force before finally saying that it doesn't actually exist.

 

Is there any context in which "weight density" is actually used? Engineering maybe?

[regentrude]

Do you mean specifically the term "weight density"?

"Weight density" - never heard it used; does he actually use pounds per volume? And he does really not mean mass density (g/cm^3)?

 

ETA: Thinking about it some more: YES, this quantity (weight per volume) actually does come up, but usually under the name "specific weight". I have come across this quite frequently in fluid mechanics. And wikipedia lists applications in soil mechanics and mechanical engineering.

 

 

About the centrifugal force: that depends entirely on your reference frame.

It does not exist in an inertial reference frame. But in a non-inertial, rotating reference frame, the centrifugal force does exist, just like the Coriolis force that is responsible for the formation of hurricanes. (I have not seen a description of hurricane formation from the point of view of an inertial reference frame without Coriolis force.) The mechanism how you get those two inertial, or pseudo, forces is the same - if you do the coordinate transformation to the rotating frame and set up Newton's law, they come from the time derivative of the unit vectors - which obviously he can not explain in a conceptual text)

The centrifugal force is, for example, responsible for a difference in free-fall acceleration between poles and equator.

 

I think he is in a very difficult position trying to include this in a conceptual text ;-)

[kiana]

I have to add this cartoon to the centrifugal force discussion: http://xkcd.com/123/

[amy58103]

Weight Density (if you mean weight/volume) is one of the basic parameters used in soil mechanics ... the "theory" behind Geotechnical Engineering, which is a sub-discipline of Civil Engineering. I use it every day at work, in many different forms ... moist unit weight of soil, dry unit weight of soil, saturated unit weight of soil, specific unit weight of soil, specific unit weight of water, maximum dry density of soil, etc.

[AngieW in Texas]

I'm glad to hear that "weight density" is actually used in some context. I have an MS in Physics and NEVER heard that term ever. My specialization was in materials science for the semiconductor industry, so it certainly never came up in grad school, but I never heard it in undergrad either.