# Density

Written by Jerry Ratzlaff on . Posted in Classical Mechanics

Density, abbreviated as $$\rho$$ (Greek symbol rho) or DENS, also called volumetric mass density or specific mass, more precisely volumetric mass density (mass density), is the ratio of the amount of matter in an object compared to its volume.  A small, heavy object, such as a rock or a lump of lead, is denser than a larger object of the same mass, such as a piece of cork or foam.

Density is a scalar quantity having direction, some of these include area, energy, entropy, length, mass, power, pressure, speed, temperature, volume, and work.

Depending on its density determines whether or not oil will sink or float on water.  Density can also be expressed as specific gravity, which is the ratio of the density of the substance as compared to a reference material at a standard set of conditions.

## Density types

• Area Density  -  Mass over a one-dimensional area.
• Bulk Density  -  The ratio total weight of soil to the total volume of soil.
• Charge Density  -  The electric charge per volume.
• Current Density  -  The ratio of electric current to area.
• Densitometry  -  Measuring the optical density of photographic paper, photographic film and x-ray film.
• Energy Density  -  Potential energy per unit volume or mass.
• Force Density  -  Force per unit volume.
• Linear Density  -  Mass over a one-dimensional line.
• Number Density  -  The number of particles per unit volume, area, or length.
• Optical Density  -  The absorbance of a material.
• Particle Density  -  Density of the particles that make up a particulate solid or a powder.
• Steam Density  -  Has a higher density than water vapor, the higher the pressure the higher the steam density.
• Vapour Density  -  A relative density used for gases.

## Density formula

$$\large{ \rho = \frac{m}{V} }$$
Symbol English Metric
$$\large{ \rho }$$   (Greek symbol rho) = density $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$
$$\large{ m }$$ = mass $$\large{lbm}$$ $$\large{kg}$$
$$\large{ V }$$ = volume $$\large{ft^3}$$ $$\large{m^3}$$