# Chemical Engineering - Fluid Mechanics - Discussion

Discussion Forum : Fluid Mechanics - Section 1 (Q.No. 4)
4.
The normal stress is the same in all directions at a point in a fluid, when the fluid is
non-viscous.
incompressible.
both (a) and (b).
having no motion of one fluid layer relative to the other.
Explanation:
No answer description is available. Let's discuss.
Discussion:
10 comments Page 1 of 1.

Shubham said:   3 months ago
Hydrostatic equilibrium fluid is at rest condition that's why the answer is D.
(1)

Kamal said:   10 months ago
Basically normal means perpendicular so doesn't move anywhere.
(1)

Jay said:   6 years ago
The principle of hydrostatic equilibrium is the fluid in which vapour liquid state is in contant. Either liquid nor vapour move untill you doesn't provide any external force.
(1)

Goutham said:   8 years ago
What is the principle of hydrostatic equilibrium?
(2)

My dear friends,

In the fluid normal stress will act only when hydrostatic force will act on fluid isn't it? and our hydrostatic force will act only when our fluid is at rest ok.
(2)

Ghazanfer Ali said:   1 decade ago
Right, as we go in the normal direction fluid velocity increases, and this is due to viscosity, so for a fluid with no viscosity, the relative motion of layers should also be zero, i.e. no change in shear stress, option A should also be correct?
(1)

If the fluid move relative to one another the shear stress must developed and the motion of the fluid influenced by shear stress.

This is known as pascal's law. Pressure is independent of orientation of area vector for a fluid at rest.
(1)

When a fluid is in motion shear stresses are developed if the particles of the fluid move relative to one another. When this happens adjacent particles have different velocities. If fluid velocity is the same at every point then there is no shear stress produced: the particles have zero relative velocity.

Any motion of different layers relative to each other corresponds to the presence and application of stress upon the fluid particles. Without the application of any stress or external force there would not be any relative motion of fluid layers.