Question

An expression for coefficient of viscosity is (if F = viscous force; A = Area, V = difference in
Velocity, x = distance between two layers)​

Answer 1

✓ An expression for coefficient of viscosity

When two parallel layers of a liquid are moving with different velocities , they experience tangential forces which tend to retardation the faster layer and accelerate the slower layer. These forces are called forces of viscosity. Consider two layers of liquid separated by a distance dz. Let v and v + dv be the velocities of two layers. So the velocity gradient is dv/dz. Let A be the surface area of the layer. The viscous force is directly proportional to the surface area A and velocity gradient dv / dz.

F ∝ A dv /dz or F = η A dv /dz

where η is a constant of viscosity for the liquid and called Coefficient of viscosity.

______________________