A fluid is defined as substance that has no fixed shape and yields easily to external pressure, a gas or especially a liquid.Fluid takes the shape of its container as it doesn’t have any shape. It has only mass, volume and density in static condition. The branch of physics dealing with the study of fluids is called hydrostatics.
Density: Mass per unit volume is density. It is denoted by ‘?’ and in SI system it is measured in unit of kilogram per cubic meter.
? = m/v.
Pressure: Force per unit area is called pressure. Pressure exerted by the liquid to the bottom of the container because of its weight. It is denoted by ‘P’ and in SI system it is measured in N/m2 (Newton per meter square) which is called Pascal.
P = F/A
Force is defined as mass with acceleration, here, m is mass and g is acceleration due to gravity.
According to the definition of density, we can change mass in terms of density ‘?’ and volume ‘V’.
We can also simplify volume in terms of height ‘h’ and area ‘A’.
There are some principles in the fluids:
It state that the pressure applied at one point in an enclosed fluid under equilibrium is transmitted equally to the all parts of the fluid.
It gives the buoyant force, which is the upward force on an object placed in a fluid. By the principle, magnitude of a buoyant force on a completely or partially submerged object is always equal to the weight of the fluid displaced by it.
If the fluid is flowing through a section of pipe with one end having smaller sectional area than the other end, velocity of the fluid in the constructed end will be greater than the velocity at the larger end. But the volume per unit time should be same at all the points in the pipe.