PROPERTIES OF FLUIDS

The properties of fluid are described below-

1] Density or mass density- Density or mass density of a fluid is defined as the ratio of mass of fluid to its volume. Thus mass per unit volume of fluid is called the density. It is denoted by ρ. The unit of mass density in SI unit is kg per cubic metre, i.e., kg/m2

The density of liquids may be considered as constant while that of gases changes with the variation of pressure and temperature.

mathematically, mass density is written as

ρ = m/v
where, m= mass of fluid
v= volume of fluid

2] Specific weight or weight density- Specific weight or weight density of a fluid is the ratio between the weight of a fluid to its volume. Thus weight per unit volume of a fluid id called weight density and is denoted by the symbol w.

Thus mathematically,

w= W/V
w= mg/v
w= ρg [ρ = m/v]
where, g= Acceleration due to gravity

3] Specific volume- Specific volume of a fluid is defined as the volume of a fluid occupied by a unit mass or volume per unit mass of a fluid is called specific volume.

Mathematically, it is expressed as

Specific volume= Volume of fluid {v}/ Mass of fluid{m}
= 1/[Mass of fluid/ volume of fluid]
= 1/ρ

Thus specific volume is the reciprocal of mass density. It is expressed as m3/kg. It is commonly applied to gases.

Also read Bernoulli's principle


4] Specific gravity- Specific gravity is defined as the ratio of the weight density of a fluid to the weight density to a standard fluid. For liquids, standard fluid id taken water and for gases, the standard fluid is taken air. Specific gravity is also called relative density. It is dimensionless quantity and is denoted by the symbol S.

mathematically,

S{for liquids}= Weight density of liquid/ Weight density of water
S{for gases} = Weight density of gas/ Weight density of air

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