![]() Specific Weight (or force per unit volume) can be expressed asĪ g = acceleration of gravity (9.807, 32.174 under normal conditions) Specific Weight is defined as weight per unit volume. See also Thermophysical Properties of Air - density, viscosity, critical temperature and pressure, triple point, enthalpi and entropi, thermal conductivity and diffusicity. Molecular weights can be used to calculate Specific Gravity if the densities of the gas and the air are evaluated at the same pressure and temperature. Ρ air = density of air (normally at NTP - 1.204 ) The Specific Gravity can be calculated as Specific Gravity of gases is normally calculated with reference to air - and defined as the ratio of the density of the gas to the density of the air - at a specified temperature and pressure. Specific Gravity for some common Materials Specific Gravities common Substances Substance See also Thermophysical Properties of Water - Density, Freezing temperature, Boiling temperature, Latent heat of melting, Latent heat of evaporation, Critical temperature. Water is normally also used as reference when calculating the specific gravity for solids. SG of a fluid has the same numerical value as its density expressed in g/mL or Mg/m 3. Since Specific Gravity - SG - is dimensionless, it has the same value in the SI system and the imperial English system (BG). It is common to use the density of water at 4 oC (39 oF) as a reference since water at this point has its highest density of 1000 kg/m 3 or 1.940 slugs/ft 3. Ρ H2O = density of water - normally at temperature 4 oC Ρ substance = density of the fluid or substance Specific Gravity (Relative Density) - SG - is a dimensionless unit defined as the ratio of the density of a substance to the density of water - at a specified temperature and can be expressed as How to measure density of liquid petroleum products.Air - Density, Specific Weight and Thermal Expantion Coefficient - variation with temperature and pressure, SI and Imperial units.Water - Density, Specific Weight and Thermal Expantion Coefficient - variation with temperature at 1, 68 and 680 atm, SI and Imperial units.Density is a physical property - constant at a given temperature and pressure - and may be helpful for identification of substances.īelow on this page: Specific gravity (relative density), Specific gravity for gases, Specific weight, Calculation examples On atomic level - particles are packed tighter inside a substance with higher density. See also Unit converter - mass and Unit converter - density Slugs can be multiplied with 32.2 for a rough value in pound-mass (lb m). Note that there is a difference between pound-force (lb f) and pound-mass (lb m). The Imperial (U.S.) units for density are slugs /ft 3 but pound-mass per cubic foot - lb m /ft 3 - is often used. What is weight and what is mass ? - the difference between weight and mass.Mass is a property and the SI unit for density is. Moist unit weight The unit weight of a soil when void spaces of the soil contain both water and air.Density is defined as mass per unit volume. In soil mechanics, specific weight may refer to: Specific weight is often used as a property of soil to solve earthwork problems. Specific weight can be used as a characteristic property of a fluid. For this reason, units are expressed as force per unit volume (e.g., N/m 3 or lbf/ft 3). In fluid mechanics, specific weight represents the force exerted by gravity on a unit volume of a fluid. ![]() Pressure may also affect values, depending upon the bulk modulus of the material, but generally, at moderate pressures, has a less significant effect than the other factors. It depends on the value of the gravitational acceleration, which varies with location. Unlike density, specific weight is not a fixed property of a material. The standard gravity is acceleration due to gravity, usually given in m/s 2, and on Earth usually taken as 9.81 m/s 2. The density of the material is defined as mass per unit volume, typically measured in kg/m 3.
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