Difference between viscosity and friction

What is Friction?

The most common resistive force we experience every day is called friction is caused by the contact of two rough surfaces.

What is Viscosity?

Viscosity is just the friction between two fluid layers when the two layers move relative to each other.

Viscosity is kind of a special case of friction.

Friction and viscosity are two properties that matter a lot. Let us have a deep insight into the difference between viscosity and friction. 

Main difference :

Friction is used to refer to forces that resist relative motion, whereas viscosity refers specifically to resistive forces that occur between layers of fluid when fluids attempt to flow.

Difference between viscosity and friction : 

  • Friction is due to the resistance of relative motion between two solid surfaces where viscosity is due to cohesion or adhesion between two surfaces.
  • The viscous force depends on the velocity gradient and area of contact and frictional force independent of the area of contact and relative velocity.
  • The force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding between them is called friction while the viscosity of a fluid is a measure of its resistance to gradual deformation through shear stress or tensile stress.
  • Friction between solid matter does not depend on speed difference while friction in fluids depends on speed between adjacent layers by means of their viscosity.
  • The viscosity of liquid decrease with increase in temperature, Where friction independent of temperature.

Similarity :
  • Both properties came in to play whenever there is relative motion.
  • Both oppose the relative motion.
  • Both depend upon the nature of the surface.
  • Both can be erased by intermolecular force.
You can also want to know the difference between related terms like the difference between viscosity and density.