as we know that viscosity is defined as the property of a fluid which offer resistance to the movement of one layer of fluid over another adjacent layer of the fluid, define viscosity mathematically

Detailed Solution:

has we know that top layer of fluids caused shear stress on adjacent lower layer while the lower layer causes shear stress on top adjacent layer. This shear stress is directly proportional to the rate of change of velocity with respect to distance between layer say y. hence shear stress ∝ du/dy, where u = velocity of flow, y =distance of adjacent layer, also du/dy = rate of change of velocity with respect to y shear stress = μ du/dy where μ = shear stress/ (du/dy) = viscosity