Viscosity- Resistance to flow of fluid is called viscosity.
Reason for viscosity- 1) Cohesive force. 2) Intermolecular momentum transfer.
If we plot a graph between perpendicular distance to solid boundary and velocity at that distance, this curve is called velocity profile (or) velocity distribution.
NEWTON’S LAW OF VISCOSITY- Newton’s law of viscosity states that shear stress is directly proportional to rate of shear strain or velocity gradient.
The equation of newton’s law of viscosity is τ = μ du/dy
Where τ= shear stress, μ= dynamic viscosity, and du/dy= velocity gradient.
Note: SI unit of dynamic viscosity is Pascal second.
Mechsiast 