What happens when fluid is at rest?

What happens when fluid is at rest?

Right Answer is:

There is no shear component


Fluid Under the action of shear Force:

  • When a solid body is under the action of this force, finite deformation will take place and reaches an equilibrium state after a certain time.
  • Depending on the magnitude of the shear force, the solid body may or may not try to come back to the original position.
  • It means that for a solid body shear force has to have a finite magnitude for its deformation. It means that with the increase of shear force, the deformation of a solid body increases after the magnitude of the shear force exceeds a certain value.
  • Further application of shear force will lead the body to permanent deformation.
  • Fluid continues in motion under the application of shear stress.
  • The deformation of a fluid body under the action of shear force continues without achieving an equilibrium state irrespective of the magnitude of the force.
  • Further, the rate of deformation of the fluid body depends on the amount of shearing force.
  • Fluid cannot sustain any shear stress when at rest.
  • Fluid deforms under very small shear stress. The fluid will not try to come back to the original position even for infinitely small shear force; instead, it tries to remain in a new position.


  • Fluid can be defined as a substance that can deform continuously under the action of a shear force; no matter how small the shear forces.
  • It means that a small shear force of negligible magnitude will cause deformation in the fluid.
  • This deformation continues until and unless the shear force is withdrawn and fluid remains at the new shape.
  • It also indicates that the fluid body does not have a shape of its own under the shear force.
  • Further, it is worthwhile to mention here that any fluid, irrespective of its viscosity, will yield in time to the slightest stress, which is not true for a solid.
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