Poise is the unit of:
Try it first: pick an option, then read the explanation.
Correct answer: C. Viscosity
Asked in S.S.C. J.E. 2009
Detailed Explanation
The poise is the traditional metric unit used to express the dynamic viscosity of liquids and gases.
Why “Viscosity” Is Correct
The poise (dyne·s/cm²) is the standard CGS unit of dynamic viscosity.
| 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. Mass density: Mass density in CGS is measured in g/cm³.
- B. Kinematic viscosity: Kinematic viscosity in CGS is measured in stokes (cm²/s).
- D. Velocity gradient: Velocity gradient is measured in s⁻¹.
Key Point
Poise is the CGS unit of dynamic viscosity (1 poise = 0.1 Pa·s).
Key Concepts for Students
- 1 poise = 1 dyne·s/cm² = 1 g/(cm·s).
- 1 centipoise (cP) = 0.01 poise = 1 mPa·s.
- Water at room temperature has a viscosity of approximately 1 cP.
Practice more: this is question 68 in Properties of Fluid MCQs – Part 5. Try the whole set and check every answer instantly.