In which of the following unit kinematic viscosity of fluid is measured?
Try it first: pick an option, then read the explanation.
Correct answer: D. stokes
Asked in SSC JE 24-01-2018 (Evening Shift)
Detailed Explanation
Transport properties have historical units in the CGS metric system that remain widely cited in technical codes and engineering literature.
Why “stokes” Is Correct
Kinematic viscosity is measured in stokes (1 stoke = 1 cm²/s = 10⁻⁴ m²/s). Centistokes (cSt) are commonly used for lubricating oils.
| Quantity | SI unit | CGS unit | Conversion |
|---|---|---|---|
| Dynamic viscosity μ | Pa·s (N·s/m²) | Poise (P) = dyne·s/cm² | 1 P = 0.1 Pa·s |
| Kinematic viscosity ν = μ/ρ | m²/s | Stoke (St) = cm²/s | 1 St = 10⁻⁴ m²/s |
| Surface tension T | N/m | dyne/cm | 1 dyne/cm = 10⁻³ N/m |
Why the Other Options Are Wrong
- A. m/s: m/s is the unit of linear velocity.
- B. m/s²: m/s² is the unit of linear acceleration.
- C. dyne: dyne is the CGS unit of force (1 dyne = 10⁻⁵ N).
Key Point
Unit of kinematic viscosity is stokes (cm²/s); 1 stoke = 10⁻⁴ m²/s.
Key Concepts for Students
- Named after Sir George Gabriel Stokes.
- Dynamic viscosity is measured in poise; kinematic viscosity is measured in stokes.
- 1 centistoke (cSt) = 1 mm²/s.
Practice more: this is question 44 in Properties of Fluid MCQs – Part 3. Try the whole set and check every answer instantly.