Numford

Properties of matterClass 11, Mechanical Properties of Fluids

Dimensional formula of Kinematic viscosity

[L2 T-1]

Symbolν SI unitsquare metre per second (m²/s)

Viscosity divided by density. It has the same dimension as the diffusion coefficient.

Derivation

How to get the dimensional formula of kinematic viscosity

  1. Start from the definition: kinematic viscosity = viscosity / density.
  2. velocity = length / time, so velocity is [L] / [T] = [L T-1].
  3. acceleration = velocity / time, so acceleration is [L T-1] / [T] = [L T-2].
  4. force = mass × acceleration, so force is [M] × [L T-2] = [M L T-2].
  5. area = length × length, so area is [L] × [L] = [L2].
  6. coefficient of viscosity = force × length / (area × velocity), so coefficient of viscosity is [M L T-2] × [L] / ([L2] × [L T-1]) = [M L-1 T-1].
  7. volume = length3, so volume is [L]3 = [L3].
  8. Put in the dimension of each part: [M L-1 T-1] / [M L-3].
  9. Add the powers of each base quantity: [L2 T-1].
Practice

Three questions on kinematic viscosity

1Which is the dimensional formula of kinematic viscosity?

2What is the SI unit of kinematic viscosity?

3Do kinematic viscosity and velocity gradient have the same dimensions?

Questions

Kinematic viscosity: quick answers

What is the dimensional formula of kinematic viscosity?

The dimensional formula of kinematic viscosity is [L² T⁻¹]. It comes from kinematic viscosity = viscosity / density.

What is the SI unit of kinematic viscosity?

The SI unit of kinematic viscosity is the square metre per second (m²/s).

Is kinematic viscosity dimensionless?

No. Kinematic viscosity has the dimensions [L² T⁻¹].

Open the dimensional formula tool