The density (ρ) of a substance of uniform composition is its mass per unit volume: ρ = m/ V. In the SI system, density is measured in units of kilograms per cubic meter.
Imagine an upright cylindrical beaker filled with a fluid. The
fluid exerts a force on the bottom of the container due to its
weight. Pressure is defined as the force per
unit area: P = F/ A
, or in terms of magnitude, P = mg/A, where mg
is the weight of the fluid. The SI unit of pressure is N/m2,
called a pascal. The pressure at the bottom of a fluid can be
expressed in terms of the density (ρ) and height (h)
of the fluid: (giancolli)