fajsúly

Fajsúly is a term used in Hungarian physics and engineering to describe how much mass a given volume of a material contains. In many contexts it is equivalent to density, the mass per unit volume. In other settings, fajsúly may refer to weight density (weight per unit volume) or to a substance’s specific gravity, which is the ratio of its density to that of water. The precise meaning can vary by field and region, so technical texts typically define the term explicitly.

In SI units the primary quantity is density, ρ, with units of kilograms per cubic meter (kg/m^3). If fajsúly is used as weight density, the units are newtons per cubic meter (N/m^3) and the relationship is γ = ρ g, where g is the acceleration due to gravity. The dimensionless specific gravity SG is defined as ρ/ρ_water, with ρ_water about 1000 kg/m^3 at 4 °C.

Typical values illustrate the concept: air ~1.2 kg/m^3, water ~1000 kg/m^3, steel ~7850 kg/m^3, tungsten ~19,000 kg/m^3. Densities vary with temperature and pressure, so precise values require conditions to be specified.

Measurement methods include direct determination by measuring mass and volume or by buoyancy-based techniques, pycnometry, and modern densimeters. For gases, densities are often estimated with the ideal gas law, while liquids and solids use liquid or solid-density methods.

Applications of fajsúly are widespread: buoyancy calculations in fluids, structural and mechanical design, HVAC and fluid dynamics, geological and material science analyses, quality control in manufacturing, and any scenario where mass per unit volume affects performance or safety. The term’s exact meaning should be defined in context to avoid ambiguity.