FLUID MECHANICS: FUNDAMENTALS
AND APPLICATIONS -
COMPREHENSIVE MASTERY
QUESTIONS AND ANSWERS
1. For a Newtonian fluid, the shear stress is linearly proportional to which of the following?
A. The total displacement of the fluid
B. The square of the velocity gradient
C. The velocity gradient perpendicular to the flow
D. The pressure gradient in the direction of flow
Answer: C
Conceptual Explanation: By definition, a Newtonian fluid follows Newton’s law of
viscosity, where shear stress is proportional to the rate of shear strain (velocity gradient).
2. In a static fluid, how does the pressure change with depth in a compressible fluid like the
atmosphere?
A. Linearly with depth
B. Logarithmically with height
,C. Pressure remains constant regardless of height
D. Exponentially with altitude (assuming isothermal conditions)
Answer: D
Conceptual Explanation: For an isothermal compressible fluid like air, the barometric
formula shows that pressure decreases exponentially with increasing altitude.
3. Which dimensionless number represents the ratio of inertial forces to surface tension
forces?
A. Reynolds number
B. Froude number
C. Weber number
D. Mach number
Answer: C
Conceptual Explanation: The Weber number (We = rhov^2L / sigma) is the ratio of
inertia to surface tension, critical in droplet formation and thin film flows.
4. Under what condition is the Bernoulli equation valid along a streamline?
A. Steady, compressible, and viscous flow
B. Unsteady, incompressible, and frictionless flow
C. Steady, incompressible, and frictionless flow
, D. Steady, incompressible, and rotational flow
Answer: C
Conceptual Explanation: The standard Bernoulli equation assumes steady flow, constant
density (incompressible), and neglect of frictional (viscous) effects.
5. What occurs to the stagnation pressure across a normal shock wave in supersonic flow?
A. It increases
B. It decreases
C. It remains constant
D. It becomes zero
Answer: B
Conceptual Explanation: While stagnation enthalpy remains constant, the stagnation
pressure always decreases across a shock wave due to the increase in entropy
(irreversibility).
6. In the context of the Navier-Stokes equations, what does the term (u dot grad)u represent?
A. Local acceleration
B. Advective (convective) acceleration
C. Viscous dissipation
D. Pressure work
AND APPLICATIONS -
COMPREHENSIVE MASTERY
QUESTIONS AND ANSWERS
1. For a Newtonian fluid, the shear stress is linearly proportional to which of the following?
A. The total displacement of the fluid
B. The square of the velocity gradient
C. The velocity gradient perpendicular to the flow
D. The pressure gradient in the direction of flow
Answer: C
Conceptual Explanation: By definition, a Newtonian fluid follows Newton’s law of
viscosity, where shear stress is proportional to the rate of shear strain (velocity gradient).
2. In a static fluid, how does the pressure change with depth in a compressible fluid like the
atmosphere?
A. Linearly with depth
B. Logarithmically with height
,C. Pressure remains constant regardless of height
D. Exponentially with altitude (assuming isothermal conditions)
Answer: D
Conceptual Explanation: For an isothermal compressible fluid like air, the barometric
formula shows that pressure decreases exponentially with increasing altitude.
3. Which dimensionless number represents the ratio of inertial forces to surface tension
forces?
A. Reynolds number
B. Froude number
C. Weber number
D. Mach number
Answer: C
Conceptual Explanation: The Weber number (We = rhov^2L / sigma) is the ratio of
inertia to surface tension, critical in droplet formation and thin film flows.
4. Under what condition is the Bernoulli equation valid along a streamline?
A. Steady, compressible, and viscous flow
B. Unsteady, incompressible, and frictionless flow
C. Steady, incompressible, and frictionless flow
, D. Steady, incompressible, and rotational flow
Answer: C
Conceptual Explanation: The standard Bernoulli equation assumes steady flow, constant
density (incompressible), and neglect of frictional (viscous) effects.
5. What occurs to the stagnation pressure across a normal shock wave in supersonic flow?
A. It increases
B. It decreases
C. It remains constant
D. It becomes zero
Answer: B
Conceptual Explanation: While stagnation enthalpy remains constant, the stagnation
pressure always decreases across a shock wave due to the increase in entropy
(irreversibility).
6. In the context of the Navier-Stokes equations, what does the term (u dot grad)u represent?
A. Local acceleration
B. Advective (convective) acceleration
C. Viscous dissipation
D. Pressure work
