Unit equivalence for dynamic viscosity:\n1 centipoise (cP) is approximately equal to which of the following?

Introduction / Context:
Dynamic viscosity appears in momentum transfer, pump sizing, and mixing problems. Engineers often need to convert between SI and English units. Knowing reliable equivalences for 1 centipoise (cP) prevents conversion errors.

Given Data / Assumptions:

• 1 poise (P) = 1 g/(cm·s).
• 1 centipoise (cP) = 0.01 P = 0.01 g/(cm·s).
• In SI, 1 cP = 1 mPa·s = 0.001 Pa·s.

Concept / Approach:
We convert 1 cP (0.001 Pa·s) to lb/(ft·hr) to match the offered options. Use the chain: Pa·s → kg/(m·s) → lb/(ft·hr). This conversion yields a convenient benchmark used widely in handbooks.

Step-by-Step Solution:

Verification / Alternative check:
Also remember equivalences: 1 cP = 0.01 g/(cm·s) and 1 cP = 1 mPa·s. While both are correct statements, only one of the given numerical English-unit options matches the standard value, namely 2.42 lb/(ft·hr).

Why Other Options Are Wrong:

• 1 g/(cm·s): This is 1 P, not 1 cP.
• 1 cSt: Kinematic viscosity; equals 1 cP only when density = 1 g/cm³ (not a general equivalence).
• 2.42 lb/(ft·s): Off by a factor of 3600 (seconds vs hours).
• 1 mPa·s: Although true, it was not among the original options in many legacy sets; if present, it would also be correct. Here the targeted numeric English-unit match is 2.42 lb/(ft·hr).

Common Pitfalls:
Confusing dynamic with kinematic viscosity; dropping the hour-to-second conversion; mistaking poise for centipoise.

Final Answer:
2.42 lb/(ft·hr)