COMPREHENSIVE FLUID MECHANICS
EXAMINATION (CHAPTERS 1-15)
QUESTIONS AND ANSWERS
1. A fluid is defined as a substance that:
A. Has a fixed volume and shape regardless of the container.
B. Can sustain a shear stress when at rest.
C. Deforms continuously under the application of a shear stress of any magnitude.
D. Always behaves as a Newtonian substance under high pressure.
Answer: C
Conceptual Explanation: By definition, a fluid (liquid or gas) cannot resist shear stress
without moving; it deforms continuously as long as the stress is applied.
2. The condition of ‘no-slip’ at a solid-fluid interface is primarily due to:
A. The pressure difference between the fluid and the wall.
B. The weight of the fluid pressing against the surface.
C. Viscous effects and molecular attraction between the fluid and the surface.
,D. The surface tension of the fluid at the boundary.
Answer: C
Conceptual Explanation: The no-slip condition states that fluid particles in direct contact
with a solid surface assume the velocity of that surface due to viscosity.
3. In a Newtonian fluid, the shear stress is:
A. Proportional to the square of the velocity gradient.
B. Inversely proportional to the dynamic viscosity.
C. Independent of the rate of deformation.
D. Linearly proportional to the rate of shear strain.
Answer: D
Conceptual Explanation: Newtonian fluids follow the relation tau = mu * (du/dy), where
shear stress is linearly proportional to the velocity gradient (strain rate).
4. Cavitation in a fluid system occurs when:
A. The dissolved gases are compressed into the liquid phase.
B. The fluid velocity reaches the speed of sound.
C. The temperature of the fluid drops below its freezing point.
D. The local pressure drops below the vapor pressure of the liquid.
Answer: D
, Conceptual Explanation: Cavitation involves the formation of vapor bubbles in a liquid
when local pressure drops below vapor pressure, followed by their violent collapse.
5. For a submerged plane surface, the center of pressure is always:
A. At the same location as the centroid of the surface.
B. Directly above the centroid of the surface.
C. At the free surface of the liquid.
D. Below the centroid of the surface.
Answer: D
Conceptual Explanation: Because pressure increases with depth, the lower half of the
surface experiences more force, shifting the center of pressure below the centroid.
6. Archimedes’ principle states that the buoyant force is equal to:
A. The weight of the object submerged.
B. The density of the fluid multiplied by the depth.
C. The weight of the fluid displaced by the body.
D. The difference between the atmospheric pressure and gauge pressure.
Answer: C
Conceptual Explanation: The buoyant force acting on a body immersed in a fluid is equal
to the weight of the fluid that the body displaces.
EXAMINATION (CHAPTERS 1-15)
QUESTIONS AND ANSWERS
1. A fluid is defined as a substance that:
A. Has a fixed volume and shape regardless of the container.
B. Can sustain a shear stress when at rest.
C. Deforms continuously under the application of a shear stress of any magnitude.
D. Always behaves as a Newtonian substance under high pressure.
Answer: C
Conceptual Explanation: By definition, a fluid (liquid or gas) cannot resist shear stress
without moving; it deforms continuously as long as the stress is applied.
2. The condition of ‘no-slip’ at a solid-fluid interface is primarily due to:
A. The pressure difference between the fluid and the wall.
B. The weight of the fluid pressing against the surface.
C. Viscous effects and molecular attraction between the fluid and the surface.
,D. The surface tension of the fluid at the boundary.
Answer: C
Conceptual Explanation: The no-slip condition states that fluid particles in direct contact
with a solid surface assume the velocity of that surface due to viscosity.
3. In a Newtonian fluid, the shear stress is:
A. Proportional to the square of the velocity gradient.
B. Inversely proportional to the dynamic viscosity.
C. Independent of the rate of deformation.
D. Linearly proportional to the rate of shear strain.
Answer: D
Conceptual Explanation: Newtonian fluids follow the relation tau = mu * (du/dy), where
shear stress is linearly proportional to the velocity gradient (strain rate).
4. Cavitation in a fluid system occurs when:
A. The dissolved gases are compressed into the liquid phase.
B. The fluid velocity reaches the speed of sound.
C. The temperature of the fluid drops below its freezing point.
D. The local pressure drops below the vapor pressure of the liquid.
Answer: D
, Conceptual Explanation: Cavitation involves the formation of vapor bubbles in a liquid
when local pressure drops below vapor pressure, followed by their violent collapse.
5. For a submerged plane surface, the center of pressure is always:
A. At the same location as the centroid of the surface.
B. Directly above the centroid of the surface.
C. At the free surface of the liquid.
D. Below the centroid of the surface.
Answer: D
Conceptual Explanation: Because pressure increases with depth, the lower half of the
surface experiences more force, shifting the center of pressure below the centroid.
6. Archimedes’ principle states that the buoyant force is equal to:
A. The weight of the object submerged.
B. The density of the fluid multiplied by the depth.
C. The weight of the fluid displaced by the body.
D. The difference between the atmospheric pressure and gauge pressure.
Answer: C
Conceptual Explanation: The buoyant force acting on a body immersed in a fluid is equal
to the weight of the fluid that the body displaces.
