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Absolute viscosity, µ

Environmental Engineering · FE Reference Handbook section

Environmental Engineering
0 formulas
10 exam-style examples
~45 min
All Environmental Engineering lectures

Core formulas for this FE topic

Definitions, applicability, units, assumptions and worked examples for each relation.

This section is conceptual; there are no equations to memorise.

Worked exam-style examples

The four ways this section is written on the real exam — thoughts first, then equations, then substitution.

Example 1
Absolute viscosity — solve for absolute viscosity — Absolute viscosity, µ

absolute viscosity of water used in settling velocity calculations Given kinematic viscosity (nu) = 0.0000 m^2/s; density (rho) = 997.1 kg/m^3, determine the absolute viscosity (mu) in Pa*s.

Given

  • kinematicviscosity(nu)=0.0000m2/skinematic viscosity (nu) = 0.0000 m^2/s
  • density(rho)=997.1kg/m3density (rho) = 997.1 kg/m^3

Find

absolute viscosity (mu), in Pa*s

Start with the thinking

  • The governing relation printed in this handbook section is Absolute viscosity.
  • Everything except mu is given, so isolate mu symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Absolute viscosity relates dynamic and kinematic viscosity of water through fluid density for environmental flow calculations.

Step-by-step solution

  1. Step 1 — State the governing relation:

    μ=νρ\mu = \nu \rho
  2. Step 2 — Rearrange symbolically for mu:

    μ=νρ\mu = \nu \rho
  3. Step 3

    Listthegivens:kinematicviscosity(nu)=0.0000m2/s,density(rho)=997.1kg/m3List the givens: kinematic viscosity (nu) = 0.0000 m^2/s, density (rho) = 997.1 kg/m^3
  4. Step 4 — Substitute the given values:

    μ=0.0000997.1\mu = 0.0000 997.1
  5. Step 5 — Evaluate:

    μ=0.0010 Pa*s\mu = 0.0010\ \text{Pa*s}
  6. Step 6 — Check: returning mu = 0.0010 Pa*s to

    μ=νρ\mu = \nu \rho

    reproduces the given quantities, and both sides carry the same units.

Answer:
μ=0.0010 Pa*s\mu = 0.0010\ \text{Pa*s}

Why the other options are there

  • 0.0020 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0005 — dropped that same factor in the other direction.
  • 0.0011 — rounded an intermediate value before the final step.

Reference: FE Handbook — Absolute (Dynamic) Viscosity

Example 2
Absolute viscosity — solve for kinematic viscosity — Absolute viscosity, µ (2)

absolute viscosity determined from kinematic viscosity and density at plant temperature Given density (rho) = 992.4 kg/m^3; absolute viscosity (mu) = 0.0014 Pa*s, determine the kinematic viscosity (nu) in m^2/s.

Given

  • density(rho)=992.4kg/m3density (rho) = 992.4 kg/m^3
  • absoluteviscosity(mu)=0.0014Pa∗sabsolute viscosity (mu) = 0.0014 Pa*s

Find

kinematic viscosity (nu), in m^2/s

Start with the thinking

  • The governing relation printed in this handbook section is Absolute viscosity.
  • Everything except nu is given, so isolate nu symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Absolute viscosity relates dynamic and kinematic viscosity of water through fluid density for environmental flow calculations.

Step-by-step solution

  1. Step 1 — State the governing relation:

    μ=νρ\mu = \nu \rho
  2. Step 2 — Rearrange symbolically for nu:

    ν=μρ\nu = \dfrac{\mu}{\rho}
  3. Step 3

    Listthegivens:density(rho)=992.4kg/m3,absoluteviscosity(mu)=0.0014Pa∗sList the givens: density (rho) = 992.4 kg/m^3, absolute viscosity (mu) = 0.0014 Pa*s
  4. Step 4 — Substitute the given values:

    ν=0.0014992.4\nu = \dfrac{0.0014}{992.4}
  5. Step 5 — Evaluate:

    \nu = 0.0000\ \text{m^2/s}
  6. Step 6 — Check: returning nu = 0.0000 m^2/s to

    μ=νρ\mu = \nu \rho

    reproduces the given quantities, and both sides carry the same units.

Answer:
\nu = 0.0000\ \text{m^2/s}

Why the other options are there

  • 0.0000 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0000 — dropped that same factor in the other direction.
  • 0.0000 — rounded an intermediate value before the final step.

Reference: FE Handbook — Absolute (Dynamic) Viscosity

Example 3
Absolute viscosity — solve for density — Absolute viscosity, µ (3)

absolute viscosity of wastewater at treatment plant operating temperature Given kinematic viscosity (nu) = 0.0000 m^2/s; absolute viscosity (mu) = 0.0015 Pa*s, determine the density (rho) in kg/m^3.

Given

  • kinematicviscosity(nu)=0.0000m2/skinematic viscosity (nu) = 0.0000 m^2/s
  • absoluteviscosity(mu)=0.0015Pa∗sabsolute viscosity (mu) = 0.0015 Pa*s

Find

density (rho), in kg/m^3

Start with the thinking

  • The governing relation printed in this handbook section is Absolute viscosity.
  • Everything except rho is given, so isolate rho symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Absolute viscosity relates dynamic and kinematic viscosity of water through fluid density for environmental flow calculations.

Step-by-step solution

  1. Step 1 — State the governing relation:

    μ=νρ\mu = \nu \rho
  2. Step 2 — Rearrange symbolically for rho:

    ρ=μν\rho = \dfrac{\mu}{\nu}
  3. Step 3

    Listthegivens:kinematicviscosity(nu)=0.0000m2/s,absoluteviscosity(mu)=0.0015Pa∗sList the givens: kinematic viscosity (nu) = 0.0000 m^2/s, absolute viscosity (mu) = 0.0015 Pa*s
  4. Step 4 — Substitute the given values:

    ρ=0.00150.0000\rho = \dfrac{0.0015}{0.0000}
  5. Step 5 — Evaluate:

    \rho = 1540\ \text{kg/m^3}
  6. Step 6 — Check: returning rho = 1,540 kg/m^3 to

    μ=νρ\mu = \nu \rho

    reproduces the given quantities, and both sides carry the same units.

Answer:
\rho = 1540\ \text{kg/m^3}

Why the other options are there

  • 3,080 — kept a factor of two that cancels in the correct rearrangement.
  • 770.0 — dropped that same factor in the other direction.
  • 1,694 — rounded an intermediate value before the final step.

Reference: FE Handbook — Absolute (Dynamic) Viscosity

Example 4
Absolute viscosity — solve for absolute viscosity (case 2) — Absolute viscosity, µ (4)

absolute viscosity of water used in settling velocity calculations Given kinematic viscosity (nu) = 0.0000 m^2/s; density (rho) = 996.4 kg/m^3, determine the absolute viscosity (mu) in Pa*s.

Given

  • kinematicviscosity(nu)=0.0000m2/skinematic viscosity (nu) = 0.0000 m^2/s
  • density(rho)=996.4kg/m3density (rho) = 996.4 kg/m^3

Find

absolute viscosity (mu), in Pa*s

Start with the thinking

  • The governing relation printed in this handbook section is Absolute viscosity.
  • Everything except mu is given, so isolate mu symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Absolute viscosity relates dynamic and kinematic viscosity of water through fluid density for environmental flow calculations.

Step-by-step solution

  1. Step 1 — State the governing relation:

    μ=νρ\mu = \nu \rho
  2. Step 2 — Rearrange symbolically for mu:

    μ=νρ\mu = \nu \rho
  3. Step 3

    Listthegivens:kinematicviscosity(nu)=0.0000m2/s,density(rho)=996.4kg/m3List the givens: kinematic viscosity (nu) = 0.0000 m^2/s, density (rho) = 996.4 kg/m^3
  4. Step 4 — Substitute the given values:

    μ=0.0000996.4\mu = 0.0000 996.4
  5. Step 5 — Evaluate:

    μ=0.0010 Pa*s\mu = 0.0010\ \text{Pa*s}
  6. Step 6 — Check: returning mu = 0.0010 Pa*s to

    μ=νρ\mu = \nu \rho

    reproduces the given quantities, and both sides carry the same units.

Answer:
μ=0.0010 Pa*s\mu = 0.0010\ \text{Pa*s}

Why the other options are there

  • 0.0020 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0005 — dropped that same factor in the other direction.
  • 0.0011 — rounded an intermediate value before the final step.

Reference: FE Handbook — Absolute (Dynamic) Viscosity

Example 5
Absolute viscosity — solve for kinematic viscosity (case 2) — Absolute viscosity, µ (5)

absolute viscosity determined from kinematic viscosity and density at plant temperature Given density (rho) = 992.7 kg/m^3; absolute viscosity (mu) = 0.0017 Pa*s, determine the kinematic viscosity (nu) in m^2/s.

Given

  • density(rho)=992.7kg/m3density (rho) = 992.7 kg/m^3
  • absoluteviscosity(mu)=0.0017Pa∗sabsolute viscosity (mu) = 0.0017 Pa*s

Find

kinematic viscosity (nu), in m^2/s

Start with the thinking

  • The governing relation printed in this handbook section is Absolute viscosity.
  • Everything except nu is given, so isolate nu symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Absolute viscosity relates dynamic and kinematic viscosity of water through fluid density for environmental flow calculations.

Step-by-step solution

  1. Step 1 — State the governing relation:

    μ=νρ\mu = \nu \rho
  2. Step 2 — Rearrange symbolically for nu:

    ν=μρ\nu = \dfrac{\mu}{\rho}
  3. Step 3

    Listthegivens:density(rho)=992.7kg/m3,absoluteviscosity(mu)=0.0017Pa∗sList the givens: density (rho) = 992.7 kg/m^3, absolute viscosity (mu) = 0.0017 Pa*s
  4. Step 4 — Substitute the given values:

    ν=0.0017992.7\nu = \dfrac{0.0017}{992.7}
  5. Step 5 — Evaluate:

    \nu = 0.0000\ \text{m^2/s}
  6. Step 6 — Check: returning nu = 0.0000 m^2/s to

    μ=νρ\mu = \nu \rho

    reproduces the given quantities, and both sides carry the same units.

Answer:
\nu = 0.0000\ \text{m^2/s}

Why the other options are there

  • 0.0000 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0000 — dropped that same factor in the other direction.
  • 0.0000 — rounded an intermediate value before the final step.

Reference: FE Handbook — Absolute (Dynamic) Viscosity

Example 6
Absolute viscosity — solve for density (case 2) — Absolute viscosity, µ (6)

absolute viscosity of wastewater at treatment plant operating temperature Given kinematic viscosity (nu) = 0.0000 m^2/s; absolute viscosity (mu) = 0.0014 Pa*s, determine the density (rho) in kg/m^3.

Given

  • kinematicviscosity(nu)=0.0000m2/skinematic viscosity (nu) = 0.0000 m^2/s
  • absoluteviscosity(mu)=0.0014Pa∗sabsolute viscosity (mu) = 0.0014 Pa*s

Find

density (rho), in kg/m^3

Start with the thinking

  • The governing relation printed in this handbook section is Absolute viscosity.
  • Everything except rho is given, so isolate rho symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Absolute viscosity relates dynamic and kinematic viscosity of water through fluid density for environmental flow calculations.

Step-by-step solution

  1. Step 1 — State the governing relation:

    μ=νρ\mu = \nu \rho
  2. Step 2 — Rearrange symbolically for rho:

    ρ=μν\rho = \dfrac{\mu}{\nu}
  3. Step 3

    Listthegivens:kinematicviscosity(nu)=0.0000m2/s,absoluteviscosity(mu)=0.0014Pa∗sList the givens: kinematic viscosity (nu) = 0.0000 m^2/s, absolute viscosity (mu) = 0.0014 Pa*s
  4. Step 4 — Substitute the given values:

    ρ=0.00140.0000\rho = \dfrac{0.0014}{0.0000}
  5. Step 5 — Evaluate:

    \rho = 695.0\ \text{kg/m^3}
  6. Step 6 — Check: returning rho = 695.0 kg/m^3 to

    μ=νρ\mu = \nu \rho

    reproduces the given quantities, and both sides carry the same units.

Answer:
\rho = 695.0\ \text{kg/m^3}

Why the other options are there

  • 1,390 — kept a factor of two that cancels in the correct rearrangement.
  • 347.5 — dropped that same factor in the other direction.
  • 764.5 — rounded an intermediate value before the final step.

Reference: FE Handbook — Absolute (Dynamic) Viscosity

Example 7
Absolute viscosity — solve for absolute viscosity (case 3) — Absolute viscosity, µ (7)

absolute viscosity of water used in settling velocity calculations Given kinematic viscosity (nu) = 0.0000 m^2/s; density (rho) = 995.7 kg/m^3, determine the absolute viscosity (mu) in Pa*s.

Given

  • kinematicviscosity(nu)=0.0000m2/skinematic viscosity (nu) = 0.0000 m^2/s
  • density(rho)=995.7kg/m3density (rho) = 995.7 kg/m^3

Find

absolute viscosity (mu), in Pa*s

Start with the thinking

  • The governing relation printed in this handbook section is Absolute viscosity.
  • Everything except mu is given, so isolate mu symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Absolute viscosity relates dynamic and kinematic viscosity of water through fluid density for environmental flow calculations.

Step-by-step solution

  1. Step 1 — State the governing relation:

    μ=νρ\mu = \nu \rho
  2. Step 2 — Rearrange symbolically for mu:

    μ=νρ\mu = \nu \rho
  3. Step 3

    Listthegivens:kinematicviscosity(nu)=0.0000m2/s,density(rho)=995.7kg/m3List the givens: kinematic viscosity (nu) = 0.0000 m^2/s, density (rho) = 995.7 kg/m^3
  4. Step 4 — Substitute the given values:

    μ=0.0000995.7\mu = 0.0000 995.7
  5. Step 5 — Evaluate:

    μ=0.0010 Pa*s\mu = 0.0010\ \text{Pa*s}
  6. Step 6 — Check: returning mu = 0.0010 Pa*s to

    μ=νρ\mu = \nu \rho

    reproduces the given quantities, and both sides carry the same units.

Answer:
μ=0.0010 Pa*s\mu = 0.0010\ \text{Pa*s}

Why the other options are there

  • 0.0020 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0005 — dropped that same factor in the other direction.
  • 0.0011 — rounded an intermediate value before the final step.

Reference: FE Handbook — Absolute (Dynamic) Viscosity

Example 8
Absolute viscosity — solve for kinematic viscosity (case 3) — Absolute viscosity, µ (8)

absolute viscosity determined from kinematic viscosity and density at plant temperature Given density (rho) = 990.5 kg/m^3; absolute viscosity (mu) = 0.0010 Pa*s, determine the kinematic viscosity (nu) in m^2/s.

Given

  • density(rho)=990.5kg/m3density (rho) = 990.5 kg/m^3
  • absoluteviscosity(mu)=0.0010Pa∗sabsolute viscosity (mu) = 0.0010 Pa*s

Find

kinematic viscosity (nu), in m^2/s

Start with the thinking

  • The governing relation printed in this handbook section is Absolute viscosity.
  • Everything except nu is given, so isolate nu symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Absolute viscosity relates dynamic and kinematic viscosity of water through fluid density for environmental flow calculations.

Step-by-step solution

  1. Step 1 — State the governing relation:

    μ=νρ\mu = \nu \rho
  2. Step 2 — Rearrange symbolically for nu:

    ν=μρ\nu = \dfrac{\mu}{\rho}
  3. Step 3

    Listthegivens:density(rho)=990.5kg/m3,absoluteviscosity(mu)=0.0010Pa∗sList the givens: density (rho) = 990.5 kg/m^3, absolute viscosity (mu) = 0.0010 Pa*s
  4. Step 4 — Substitute the given values:

    ν=0.0010990.5\nu = \dfrac{0.0010}{990.5}
  5. Step 5 — Evaluate:

    \nu = 0.0000\ \text{m^2/s}
  6. Step 6 — Check: returning nu = 0.0000 m^2/s to

    μ=νρ\mu = \nu \rho

    reproduces the given quantities, and both sides carry the same units.

Answer:
\nu = 0.0000\ \text{m^2/s}

Why the other options are there

  • 0.0000 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0000 — dropped that same factor in the other direction.
  • 0.0000 — rounded an intermediate value before the final step.

Reference: FE Handbook — Absolute (Dynamic) Viscosity

Example 9
Absolute viscosity — solve for density (case 3) — Absolute viscosity, µ (9)

absolute viscosity of wastewater at treatment plant operating temperature Given kinematic viscosity (nu) = 0.0000 m^2/s; absolute viscosity (mu) = 0.0012 Pa*s, determine the density (rho) in kg/m^3.

Given

  • kinematicviscosity(nu)=0.0000m2/skinematic viscosity (nu) = 0.0000 m^2/s
  • absoluteviscosity(mu)=0.0012Pa∗sabsolute viscosity (mu) = 0.0012 Pa*s

Find

density (rho), in kg/m^3

Start with the thinking

  • The governing relation printed in this handbook section is Absolute viscosity.
  • Everything except rho is given, so isolate rho symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Absolute viscosity relates dynamic and kinematic viscosity of water through fluid density for environmental flow calculations.

Step-by-step solution

  1. Step 1 — State the governing relation:

    μ=νρ\mu = \nu \rho
  2. Step 2 — Rearrange symbolically for rho:

    ρ=μν\rho = \dfrac{\mu}{\nu}
  3. Step 3

    Listthegivens:kinematicviscosity(nu)=0.0000m2/s,absoluteviscosity(mu)=0.0012Pa∗sList the givens: kinematic viscosity (nu) = 0.0000 m^2/s, absolute viscosity (mu) = 0.0012 Pa*s
  4. Step 4 — Substitute the given values:

    ρ=0.00120.0000\rho = \dfrac{0.0012}{0.0000}
  5. Step 5 — Evaluate:

    \rho = 1220\ \text{kg/m^3}
  6. Step 6 — Check: returning rho = 1,220 kg/m^3 to

    μ=νρ\mu = \nu \rho

    reproduces the given quantities, and both sides carry the same units.

Answer:
\rho = 1220\ \text{kg/m^3}

Why the other options are there

  • 2,440 — kept a factor of two that cancels in the correct rearrangement.
  • 610.0 — dropped that same factor in the other direction.
  • 1,342 — rounded an intermediate value before the final step.

Reference: FE Handbook — Absolute (Dynamic) Viscosity

Example 10
Absolute viscosity — solve for absolute viscosity (case 4) — Absolute viscosity, µ (10)

absolute viscosity of water used in settling velocity calculations Given kinematic viscosity (nu) = 0.0000 m^2/s; density (rho) = 996.8 kg/m^3, determine the absolute viscosity (mu) in Pa*s.

Given

  • kinematicviscosity(nu)=0.0000m2/skinematic viscosity (nu) = 0.0000 m^2/s
  • density(rho)=996.8kg/m3density (rho) = 996.8 kg/m^3

Find

absolute viscosity (mu), in Pa*s

Start with the thinking

  • The governing relation printed in this handbook section is Absolute viscosity.
  • Everything except mu is given, so isolate mu symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Absolute viscosity relates dynamic and kinematic viscosity of water through fluid density for environmental flow calculations.

Step-by-step solution

  1. Step 1 — State the governing relation:

    μ=νρ\mu = \nu \rho
  2. Step 2 — Rearrange symbolically for mu:

    μ=νρ\mu = \nu \rho
  3. Step 3

    Listthegivens:kinematicviscosity(nu)=0.0000m2/s,density(rho)=996.8kg/m3List the givens: kinematic viscosity (nu) = 0.0000 m^2/s, density (rho) = 996.8 kg/m^3
  4. Step 4 — Substitute the given values:

    μ=0.0000996.8\mu = 0.0000 996.8
  5. Step 5 — Evaluate:

    μ=0.0020 Pa*s\mu = 0.0020\ \text{Pa*s}
  6. Step 6 — Check: returning mu = 0.0020 Pa*s to

    μ=νρ\mu = \nu \rho

    reproduces the given quantities, and both sides carry the same units.

Answer:
μ=0.0020 Pa*s\mu = 0.0020\ \text{Pa*s}

Why the other options are there

  • 0.0040 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0010 — dropped that same factor in the other direction.
  • 0.0022 — rounded an intermediate value before the final step.

Reference: FE Handbook — Absolute (Dynamic) Viscosity

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