Question

The SI unit of kinematic viscosity is:
1. N-s / m²
2. dyne-s / m²
3. cm² / s
4. m² / s

Answer 1

Correct Answer - Option 4 : m² / s

Explanation:

Kinematic viscosity:

Kinematic viscosity is defined as the ratio of dynamic viscosity and density of the fluid.

\(kinematic~ viscosity= \frac {dynamic ~ viscocity}{density ~of ~fluid}\)

\(ν = \frac {μ}{ρ }\)

• SI unit = m2 / s 
• CGS unit = Stokes or cm2 / s
• 1 Stoke = 10-4 m2 / s

Dynamic Viscosity ( µ )

• Viscosity can be defined as the measure of a fluid's resistance to deformation at a given flow.
• Caused by friction within a fluid.
• Result of intermolecular forces between the particles within a fluid.
• SI unit N-s/m2 or Pa-s.

Shear stress is given by,

\(Shear\;stress = \;\mu \;\frac{{du}}{{dy}}\)

where,

µ = Dynamic Viscosity of fluid

\(\frac{u}{y}\)= Rate of shear deformation