In physics/maths, density is defined as mass divided by?
Density Density The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is "ρ" (the lower case Greek letter rho), although the Latin letter "D" can also be used. Mathematically, density is defined as mass divided by volume: where "ρ" is the density, "m" is the mass, and "V" is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume, although this is scientifically inaccurate – this quantity is more specifically
Sectional density Sectional density Sectional density is the ratio of an object's mass to its cross-sectional area with respect to a given axis. It conveys how well an object's mass is distributed (by its shape) to overcome resistance along that axis. For illustration, a nail can penetrate a target medium with its pointed end first with less force than a coin of the same mass lying flat on the target medium. Sectional density is used in gun ballistics. It is defined either as a projectile's mass divided by its cross sectional area, or as a projectile's mass "in pounds" divided by the