Fluid Properties MCQ with answer and solution

Concept

Physical distinction between dynamic and kinematic viscosity

Formula

ν = μ / ρ

Step-by-step solution

1. Dynamic viscosity (μ) measures a fluid's internal resistance to shear flow or tangential deformation. 2. Kinematic viscosity (ν = μ / ρ) is the ratio of viscous to inertial forces and represents resistance to gravity-driven flow. 3. Statement (i) claims dynamic viscosity measures gravity-driven flow, which is incorrect. 4. Statement (ii) claims kinematic viscosity measures internal resistance, which is incorrect. 5. Because both statements swap the physical definitions, neither is true. Answer: D

Explanation

Dynamic viscosity (μ) measures a fluid's internal tangential resistance to shear deformation or flow. Kinematic viscosity (ν = μ / ρ) is the ratio of dynamic viscosity to fluid density and represents the fluid's resistive flow under gravitational body forces. Because statement i swaps kinematic viscosity for dynamic, and statement ii reverses the roles, neither statement is true.

Why the other options are wrong

A) Statement (i) is false because flow under gravity relates to kinematic viscosity. B) Statement (ii) is false because internal shear resistance is measured by dynamic viscosity. C) Both statements incorrectly interchange the terms.

Shortcut

Dynamic (μ) = Internal shear resistance; Kinematic (ν) = Flow under gravity (scaled by density).

Common mistake

Confusing dynamic and kinematic viscosity definitions by failing to recognize they have been swapped.