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  1. #1
      Eiman
    Jul 2011
    -
    14,750


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    A
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    / 3 = / 3


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    = 5 105 / 2
    = 105 5



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    Specific Gravity


    Density


    The density is defined as a mediums mass per unit volume. Mass is a property.

    • Mass and Weight - the Difference! - What is weight and what is mass? An explanation of the difference between weight and mass.

    Mass can be expressed as:
    ρ = m / V (1)
    where
    ρ = density
    m = mass
    V = volume
    The SI units for density are kg/m3. The imperial (BG) units are lb/ft3 (slugs/ft3). While people often use pounds per cubic foot as a measure of density in the U.S., pounds are really a measure of force, not mass. Slugs are the correct measure of mass. You can multiply slugs by 32.2 for a rough value in pounds.
    • Unit converter for other units

    The higher the density, the tighter the particles are packed inside the substance. Density is a physical

    property constant at a given temperature and density can help to identify a substance.

    • Densities and material properties for different materials

    Example - Use the Density to Identify the Material:

    An unknown liquid substance has a mass of 18,5 g and occupies a volume of 23,4 ml. (milliliter)
    The density can be calculated as:
    ρ = [18.5 (g) / 1000 (g/kg)] / [23.4 (ml) / 1000 (ml/l) 1000 (l/m3) ]
    = 18.5 10-3 (kg) / 23.4 10-6 (m3)
    = 790 kg/m3
    If we look up densities of some common substances, we find that ethyl alcohol, or ethanol, has a density of 790 kg/m3. Our unknown liquid may likely be ethyl alcohol!
    Example - Use Density to Calculate Mass of a Volume

    The density of titanium is 4507 kg/m3 . Calculate the mass of 0,17 m3 titanium!
    m = 0.17 (m3) 4507 (kg/m3) = 766.2 kg
    Specific Weight


    Specific Weight is defined as weight per unit volume. Weight is a force.

    • Mass and Weight - the Difference! - What is weight and what is mass? An explanation of the difference between weight and mass.

    Specific Weight can be expressed as:
    γ = ρ g (2)
    where
    γ = specific weight
    g = acceleration of gravity
    The SI-units of specific weight are kN/m3. The imperial units are lb/ft3.
    The local acceleration g is under normal conditions 9.807 m/s2 in SI-units and 32.174 ft/s2 in imperial units.
    Example - Specific Weight Water

    Specific weight for water at 60 oF is 62.4 lb/ft3 in imperial units and 9.80 kN/m3 in SI-units.
    Example - Specific Weight Some other Materials


    Specific Weight - γImperial Units (lb/ft3) SI Units (kN/m3) Ethyl Alcohol49.37.74Gasoline42.56.67Glycerin78.612.4Mer cury847133SAE 20 Oil578.95Seawater6410.1Water62.49.80

    • Material Properties

    Specific Gravity

    Specific Gravity is dimensionless unit defined as the ratio of density of the material to the density of water at a specified temperature. Specific Gravity can be expressed as:
    SG = = ρ / ρH2O (3)
    where
    SG = specific gravity
    ρ = density of fluid
    ρH2O = density of water
    It is common to use the density of water at 4 oC (39 F) as reference - at this point the density of water is at the highest.
    • Thermal Properties of Water Density, Freezing temperature, Boiling temperature, Latent heat of melting, Latent heat of evaporation, Critical temperature ....

    Since Specific Weight is dimensionless it has the same value in the metric SI system as in the imperial english system (BG).
    At the reference point specific gravity has same numerically value as density.
    Example - Specific Gravity

    If the density of iron is 7850 kg/m3, 7.85 grams per cubic millimeter, 7.85 kilograms per liter, or 7.85 metric tons per cubic meter - the specific gravity of iron is:
    SG = 7850 kg/m3/ 1000 kg/m3 = 7.85
    where the density of water is 1000 kg/m3.








    1000
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  2. #2

  3. #3

    Jul 2012
    5,302

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