FLUID MECHANICS: FUNDAMENTALS
AND APPLICATIONS (6TH ED.)
COMPREHENSIVE EXAM QUESTIONS
AND ANSWERS
1. Which of the following best defines a fluid according to its behavior under stress?
A. A substance that deforms continuously under the application of a shear stress, no matter
how small.
B. A substance that can resist a shear stress by static deformation.
C. A substance that only deforms under a normal stress.
D. A substance that has a fixed shape and volume under standard conditions.
Answer: A
Conceptual Explanation: By definition, a fluid is a substance that deforms continuously
under the application of a shear (tangential) stress, regardless of the magnitude of that
stress.
2. The no-slip condition in fluid mechanics implies that:
A. There is no friction between the fluid and the wall.
,B. The pressure at the wall is always equal to the atmospheric pressure.
C. A fluid in motion cannot slide over a solid surface; its velocity at the surface is zero
relative to the surface.
D. The fluid velocity is maximum at the solid boundary.
Answer: C
Conceptual Explanation: The no-slip condition states that a fluid in direct contact with a
solid surface ‘sticks’ to it due to viscous effects, meaning its velocity relative to the
boundary is zero.
3. How does the dynamic viscosity of a liquid typically change with an increase in
temperature?
A. It increases linearly.
B. It remains constant.
C. It increases exponentially.
D. It decreases.
Answer: D
Conceptual Explanation: In liquids, viscosity is primarily due to intermolecular cohesive
forces, which weaken as temperature increases, leading to a decrease in viscosity.
4. Cavitation in a fluid system occurs when:
A. The fluid temperature reaches the boiling point at atmospheric pressure.
, B. The density of the fluid increases suddenly.
C. The fluid velocity becomes supersonic.
D. The local pressure drops below the vapor pressure of the liquid at the given
temperature.
Answer: D
Conceptual Explanation: Cavitation is the formation of vapor bubbles in a liquid when the
local pressure falls below the vapor pressure (𝑃𝑣 ) at that temperature.
5. 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 = 𝜌𝑉 2 𝐿/𝜎) characterizes the relative
importance of inertial forces to surface tension forces.
6. According to Pascal’s Law, for a fluid at rest in a closed container:
A. Pressure is higher at the top than the bottom.
B. Pressure changes linearly with horizontal distance.
AND APPLICATIONS (6TH ED.)
COMPREHENSIVE EXAM QUESTIONS
AND ANSWERS
1. Which of the following best defines a fluid according to its behavior under stress?
A. A substance that deforms continuously under the application of a shear stress, no matter
how small.
B. A substance that can resist a shear stress by static deformation.
C. A substance that only deforms under a normal stress.
D. A substance that has a fixed shape and volume under standard conditions.
Answer: A
Conceptual Explanation: By definition, a fluid is a substance that deforms continuously
under the application of a shear (tangential) stress, regardless of the magnitude of that
stress.
2. The no-slip condition in fluid mechanics implies that:
A. There is no friction between the fluid and the wall.
,B. The pressure at the wall is always equal to the atmospheric pressure.
C. A fluid in motion cannot slide over a solid surface; its velocity at the surface is zero
relative to the surface.
D. The fluid velocity is maximum at the solid boundary.
Answer: C
Conceptual Explanation: The no-slip condition states that a fluid in direct contact with a
solid surface ‘sticks’ to it due to viscous effects, meaning its velocity relative to the
boundary is zero.
3. How does the dynamic viscosity of a liquid typically change with an increase in
temperature?
A. It increases linearly.
B. It remains constant.
C. It increases exponentially.
D. It decreases.
Answer: D
Conceptual Explanation: In liquids, viscosity is primarily due to intermolecular cohesive
forces, which weaken as temperature increases, leading to a decrease in viscosity.
4. Cavitation in a fluid system occurs when:
A. The fluid temperature reaches the boiling point at atmospheric pressure.
, B. The density of the fluid increases suddenly.
C. The fluid velocity becomes supersonic.
D. The local pressure drops below the vapor pressure of the liquid at the given
temperature.
Answer: D
Conceptual Explanation: Cavitation is the formation of vapor bubbles in a liquid when the
local pressure falls below the vapor pressure (𝑃𝑣 ) at that temperature.
5. 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 = 𝜌𝑉 2 𝐿/𝜎) characterizes the relative
importance of inertial forces to surface tension forces.
6. According to Pascal’s Law, for a fluid at rest in a closed container:
A. Pressure is higher at the top than the bottom.
B. Pressure changes linearly with horizontal distance.
