Basic fluid -2

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Define density or mass density.
Density of a fluid is defined as the ratio of the mass of a fluid to its volume.
Density, ρ = mass/volume (Kg/m3)
ρ water = 1000 Kg/m3

Define specific weight or weight density.
Specific weight or weight density of a fluid is defined as the ratio between the weight of a fluid to its volume.
Specific weight, γ = weight/volume (N/m3)
γ = ρg
γwater = 9810 N/m3

Define specific volume.
Specific volume of a fluid is defined as the volume of fluid occupied by an unit wt or unit mass of a fluid.

Specific volume vs = volume/ wt = 1/γ = 1/ρg      ----- for liquids
Specific volume vs = volume/ mass = 1/ρ   ----- for gases

What is specific gravity?

Specific Gravity = Weight of the substance/ Weight of an equal volume of   water

 OR
Specific Gravity = Density of the substance/Density of water


The same formulas are used to find the density of gases by substituting air for water. A device called a hydrometer is used for measuring specific gravity of liquids.

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