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Density (volumetric mass density or specific mass) is a substance's mass per unit of volume. ... The mass is normally measured with a scale or balance; ...
Relative density ( ) or specific gravity ( ) is a dimensionless quantity, as it is the ratio of either densities or weights. where is relative density, is the density of the substance being measured, and is the density of the reference. (By convention , the Greek letter rho, denotes density.) The reference material can be indicated using ...
Density meter. A density meter ( densimeter) is a device which measures the density of an object or material. Density is usually abbreviated as either or . Typically, density either has the units of or . The most basic principle of how density is calculated is by the formula: Where: = the density of the sample. = the mass of the sample.
The area density (also known as areal density, surface density, superficial density, areic density, mass thickness, column density, or density thickness) of a two-dimensional object is calculated as the mass per unit area. The SI derived unit is the kilogram per square metre (kg·m −2 ). A related area number density can be defined by ...
Air density, like air pressure, decreases with increasing altitude. It also changes with variations in atmospheric pressure, temperature and humidity. At 101.325 kPa (abs) and 20 °C (68 °F), air has a density of approximately 1.204 kg/m (0.0752 lb/cu ft), according to the International Standard Atmosphere (ISA).
In SI units, number density is measured in m −3, although cm −3 is often used. However, these units are not quite practical when dealing with atoms or molecules of gases , liquids or solids at room temperature and atmospheric pressure , because the resulting numbers are extremely large (on the order of 10 20 ).
The linear density, represented by λ, indicates the amount of a quantity, indicated by m, per unit length along a single dimension. Linear density is the measure of a quantity of any characteristic value per unit of length. Linear mass density ( titer in textile engineering, the amount of mass per unit length) and linear charge density (the ...
Population density is the number of people per unit of area, usually transcribed as "per square kilometer" or square mile, and which may include or exclude, for example, areas of water or glaciers. Commonly this is calculated for a county, city, country, another territory or the entire world . The world's population is around 8,000,000,000 [3 ...