Density
The density at all points of a homogeneous object equals its total mass divided by its total volume. The mass is normally measured with a scale or balance; the volume may be measured directly (from the geometry of the object) or by the displacement of a fluid. To determine the density of a liquid or a gas, a hydrometer, a dasymeter or a Coriolis flow meter may be used, respectively. Similarly, hydrostatic weighing uses the displacement of water due to a submerged object to determine the density of the object.
Settling
where "w" is the settling velocity, "ρ" is density (the subscripts "p" and "f" indicate particle and fluid respectively), "g" is the acceleration due to gravity, "r" is the radius of the particle and "μ" is the dynamic viscosity of the fluid.