In the CGS unit system, “poise” is the unit of which fluid property?

Introduction / Context:
Engineering data often report viscosities in different unit systems. Knowing whether a given unit refers to dynamic or kinematic viscosity prevents order-of-magnitude errors in Reynolds number and pressure-drop calculations.

Given Data / Assumptions:

• CGS (centimetre–gram–second) system.
• Dynamic viscosity μ and kinematic viscosity ν are distinct.

Concept / Approach:

Dynamic viscosity μ in CGS is measured in poise (P). Kinematic viscosity ν = μ/ρ has unit stoke (St) = cm^2/s. In practice, centipoise (cP) and centistoke (cSt) are frequently used (1 P = 100 cP; 1 St = 100 cSt).

Step-by-Step Solution:

Verification / Alternative check:

Dimensional breakdown: μ has units of shear stress divided by velocity gradient, which yields M L^-1 T^-1, consistent with g/(cm·s) in CGS.

Why Other Options Are Wrong:

(b) Velocity gradient has units s^-1, not poise. (c) Density has g/cm^3. (d) Kinematic viscosity uses stokes, not poise. (e) Surface tension uses dyn/cm.

Common Pitfalls:

Confusing cP and P (factor 100); mixing dynamic and kinematic viscosity when computing Reynolds number Re = V L / ν.

Final Answer:

Viscosity (dynamic viscosity)