Mass = Volume x Density

Mass/volume=density
Mass=volume X density
Mass=volume X mass/volume
SO...
If we have grams for mass and inches cubed you would have density measure of grams/inch cubed

You can use any measure for mass or volume but the density MUST be that mass unit/the volume unit you used.

Generally you will use grams and centimeters cubed.

Right. Metric is always better for any scientific work, and never try to mix them together.

Long time; no see, El-Diablo.

Yeah I just forgot about A2K and remembered it a couple days ago lol.

Best Units
While I agree that you should generally use metric, the problem you are trying to solve uses a lot of old English units, so you should probably go with pounds and feet. All the length units should be convertable into feet. All the weight units into pounds.

Engineer,

Mass is not the same as weight.

In the metric system mass is measured in kilograms (or grams) and weight is measured in newtons.

In the "old English" system weight is measured in pounds. The unit for mass in slugs.

In any scientific application there an important difference between newtons/cm^3 and gm/cm^3.

nofx,

In your class you will almost always use gm/cm^3. You can correctly use any unit of mass and any unit of volume (density will always be a unit of mass over a unit of volume).

I challenge anyone to give me a good reason that one can't use kg/cubic_foot, other than that it sounds a bit strange. Scientifically and mathematicall there is no problem with using "mixed" units provided you keep them straight.

Two types of Pounds


In the English system taught to me, we used Pounds(force) and Pounds(mass). I've never seen slugs used in engineering. Maybe it's just a US thing.

OK, but to a physicist, using the same unit for weight and mass is very troubling.

Yes, but consider the word 'moot.' It can mean something is completely irrrelevant, or it can mean the main point.

Yes, it sucks


It's not exactly helpful to an engineer either though it is not the same unit, rather two units with the same name. One pound (force) is 4.45 newtons while one pound (mass) is .454 kilograms. It does have one advantage. One pound mass under one g of acceleration yields one pound force.

What units?
Nof,
Who cares what units? Now if it is a chemistry or physics class it might be useful to keep the same MKS or CGS units. that is Meters-Kilograms-Seconds or Centimeter-Gram-Second. If the prof cares, make sure your units are consistent.