define- fluid, density,weight density,specific volume,specific gravity property of fluid

1. what is fluid.

Fluid mechanics is the branch of the scince that deals with the fluid's behavior (liquid or gases) both in rest and in motion. This branch of science is therefore concerned with the static, kinematic and dynamic elements of fluids.

Rest fluid research is called static fluid study. Fluid in movement research where pressure force is not regarded is called fluid kinematics, and if pressure force is also regarded for liquids in movement, that branch of science is called fluid dynamics.

2.  properties of fluid.

(a). density or mass density:-

(b). specific weight or weight density:-

(c). specific volume:-

(d). specific gravity:-

(a). density or mass density:-

The density or mass density of the fluid is described as the proportion of the mass of the fluid to its volume, hence the density of the mass per unit volume of the fluid.

it is denoted by the symbol rho( ρ).

the unit of mass density in SI unit is kg/cubic metre(kg/m³⁾

density, ρ  =m/v

 the value of density of water is 1000 kg/m³

(b). specific weight or weight density:-
Specific liquid weight or weight density is the proportion of the liquid's weight to its volume. Thus weight per unit volume of the fluid is referred to as weight density, and the symbol w denotes it.


weight density w = W/V
OR                      w =  ρg

the value of specific weight or weight density (w) for water is 9.81×1000 N/m³ in SI unit.

(c). specific volume:-

Specific fluid volume is defined as the volume of the fluid occupied by the unit mass or volume per unit mass of the fluid is referred to as the specific volume.

specific volume = V/M

thus,specific volume is the reciprocal of mass density.

it is expressed as m³/kg. it is commonly applied to gases.

(d). specific gravity:-

Specific gravity is described as the proportion of the fluid's weight density to the normal fluid's weight density. For liquid, water is taken as normal fluid and air is taken as normal fluid for gases. Also known as relative density is specific gravity. The symbol S is denoted.