Which of the following is measured in the poise?
Try it first: pick an option, then read the explanation.
Correct answer: A. Dynamic viscosity
Asked in SSC JE 27-01-2018 (Morning Shift)
Detailed Explanation
The poise is the recognized CGS unit of dynamic (absolute) viscosity, named in honor of the French physician and physiologist Jean Léonard Marie Poiseuille.
Why “Dynamic viscosity” Is Correct
Dynamic viscosity is measured in poise (1 poise = 1 dyne·s/cm² = 0.1 N·s/m²). Centipoise (cP) is widely used for liquid viscosities.
| 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
- B. Kinematic viscosity: Kinematic viscosity is measured in stokes (cm²/s), not poise.
- C. Velocity of flow: Velocity of flow is measured in m/s or cm/s.
- D. Discharge: Discharge is measured in m³/s or litres/s.
Key Point
Dynamic viscosity is measured in poise (CGS) or Pa·s (SI).
Key Concepts for Students
- 1 poise = 1 dyne·s/cm² = 0.1 Pa·s.
- 1 centipoise (cP) = 10⁻² poise = 1 mPa·s.
- Water at 20°C has viscosity ≈ 1.002 cP.
Practice more: this is question 37 in Properties of Fluid MCQs – Part 3. Try the whole set and check every answer instantly.