Units – the meaning of the stoke (St) “Stoke” refers to which of the following physical quantities and unit systems?

Introduction:
Engineering problems often mix unit systems. This question checks whether you can associate the legacy C.G.S. unit “stoke” with the correct property in fluid mechanics.

Given Data / Assumptions:

• C.G.S. (centimetre–gram–second) and S.I./M.K.S. systems are in view.
• Kinematic viscosity (nu) and dynamic viscosity (mu) are distinct.
• Standard relationships between units apply.

Concept / Approach:
Kinematic viscosity nu = mu / rho. In the C.G.S. system, nu is measured in stokes (St) where 1 St = 1 cm^2/s. In S.I., kinematic viscosity uses m^2/s (no special named unit). Dynamic viscosity uses poise (P) in C.G.S. and Pa·s in S.I.

Step-by-Step Solution:
1) Identify property: kinematic vs dynamic viscosity.2) Recall the C.G.S. unit name: 1 St = 1 cm^2/s for nu.3) Therefore “stoke” corresponds to kinematic viscosity in C.G.S. units.

Verification / Alternative check:
Conversion: 1 St = 10^-4 m^2/s. Typical light oils: nu ~ a few cSt (centistokes), consistent with practice.

Why Other Options Are Wrong:

• M.K.S. kinematic viscosity: uses m^2/s without the name “stoke”.
• M.K.S. dynamic viscosity: unit is N·s/m^2 or Pa·s (S.I.).
• S.I. dynamic viscosity: Pa·s, not stoke.

Common Pitfalls:
Confusing poise (dynamic viscosity) with stoke (kinematic viscosity); mixing cSt with cP.

Final Answer:
kinematic viscosity in C.G.S. units