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Density is a measure of how tightly-packed material is
within an object. It is computed using the formula
Density = M / V
where M is the mass of the object (the amount of material
in the object, usually measured in grams, gm) and V is the
volume of the object (the amount of space it takes up,
usually measured in cubic centimeters, cm3). The
units of density are thus grams per cubic centimeter,
gm/cm3
Most of the objects we will be considering will be
spheres (or nearly so), so their volumes can be computed
using the formula for the volume of a sphere:
V = (4/3)(pi)R3
where R is the radius of the sphere (in cm) and (pi) is
equal to 3.14.
For reference, the density of pure water is 1
gm/cm3 (by definition), of rock around 3
gm/cm3, and of iron around 10
gm/cm3.
Sample Calculations
To see some sample calculations with density, click on
the examples below:
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Updated 7/7/06
By James
E. Heath