Units check — kinematic vs dynamic viscosity: Which of the following is not a unit of kinematic viscosity?

Introduction / Context:Viscosity describes a fluid’s resistance to flow and appears in transport correlations and Reynolds-number evaluation. Two related properties exist: dynamic (absolute) viscosity μ and kinematic viscosity ν, related by ν = μ/ρ. Confusing their units can lead to incorrect dimensionless groups and erroneous designs.

Given Data / Assumptions:

• Kinematic viscosity ν has SI units m^2/s; CGS unit is the stoke (1 St = 1 cm^2/s).
• Dynamic viscosity μ has SI units Pa·s; CGS unit is the poise (1 P = 1 g/(cm·s)).

Concept / Approach:Identify which listed units represent ν. Since ν is an area per time, any unit equivalent to length^2/time qualifies. “Stoke” and “cm^2/s” are standard for kinematic viscosity in CGS. “Poise,” however, belongs to dynamic viscosity and therefore is not a kinematic viscosity unit.

Step-by-Step Solution:Recall definitions: ν = μ/ρ; μ units differ from ν units.Map units: Poise → dynamic; Stoke and cm^2/s → kinematic.Select the option that is not a kinematic unit: Poise.

Verification / Alternative check:1 St = 100 cSt (centistokes); water at ~20°C has ν ≈ 1 cSt; μ for water is ≈ 1 cP (centipoise). The factor-of-100 scaling between cSt and cP reflects ρ ≈ 1 g/cm^3.

Why Other Options Are Wrong:Stoke and cm^2/s are exactly kinematic viscosity units.“None of these” would imply all are units of ν, which is false.

Common Pitfalls:Interchanging cP and cSt; forgetting density links μ and ν.

Final Answer:Poise