Civil Engineering MCQ – Fluid Mechanics

Here’s a set of 25 multiple-choice questions (MCQs) on Fluid Mechanics, tailored for civil engineering beginners. Each question has four options, an answer, and a brief explanation.

1. What is the study of fluid mechanics primarily concerned with?

a) The behavior of gases and liquids at rest and in motion
b) The study of solid materials only
c) The design of electrical circuits
d) The analysis of chemical reactions in fluids

Answer:

a) The behavior of gases and liquids at rest and in motion

Explanation:

Fluid mechanics is the branch of physics concerned with the mechanics of fluids (liquids, gases, and plasmas) and the forces on them, both at rest and in motion.

2. What is the principle behind Bernoulli's equation in fluid mechanics?

a) The conservation of energy in a flowing fluid
b) The relationship between fluid velocity and pressure
c) The measurement of fluid density
d) The calculation of fluid viscosity

Answer:

a) The conservation of energy in a flowing fluid

Explanation:

Bernoulli's equation in fluid mechanics is based on the conservation of energy, stating that the total energy in a flowing fluid remains constant along its path.

3. What does viscosity measure in a fluid?

a) The fluid’s temperature
b) The fluid's resistance to flow
c) The fluid’s color
d) The fluid’s taste

Answer:

b) The fluid's resistance to flow

Explanation:

Viscosity is a measure of a fluid's resistance to deformation at a given rate, often described as its "thickness" or "internal friction".

4. What is laminar flow in fluid mechanics?

a) A type of flow where the fluid moves in parallel layers
b) A chaotic flow pattern
c) The flow of solids
d) The flow under high pressure only

Answer:

a) A type of flow where the fluid moves in parallel layers

Explanation:

Laminar flow is characterized by smooth or in parallel layers flow of fluid, with little or no mixing between the layers.

5. What is the purpose of a venturi meter in fluid mechanics?

a) To measure the temperature of the fluid
b) To measure the velocity of flowing fluid
c) To change the direction of the fluid flow
d) To store fluids

Answer:

b) To measure the velocity of flowing fluid

Explanation:

A venturi meter is a device used to measure the flow rate or velocity of a fluid through a pipeline.

6. What is hydrostatic pressure?

a) The pressure exerted by a fluid in motion
b) The pressure exerted by a fluid at rest
c) The pressure due to the fluid’s temperature
d) The pressure due to the fluid’s color

Answer:

b) The pressure exerted by a fluid at rest

Explanation:

Hydrostatic pressure is the pressure exerted by a fluid at rest, due to the force of gravity.

7. What does Reynolds number signify in fluid mechanics?

a) The type of fluid
b) The color of the fluid
c) The temperature of the fluid
d) The type of flow (laminar or turbulent)

Answer:

d) The type of flow (laminar or turbulent)

Explanation:

Reynolds number is a dimensionless quantity used to predict flow patterns in different fluid flow situations, indicating whether the flow is laminar or turbulent.

8. What is the primary factor affecting the buoyancy of an object in a fluid?

a) The object’s weight
b) The object’s color
c) The fluid’s viscosity
d) The fluid’s density

Answer:

d) The fluid’s density

Explanation:

Buoyancy, the force exerted on an object that is partly or wholly immersed in a fluid, is primarily affected by the density of the fluid.

9. In fluid mechanics, what is a vortex?

a) A device to measure fluid velocity
b) A flow pattern where fluid rotates around an axis
c) A method to increase fluid pressure
d) A type of fluid filter

Answer:

b) A flow pattern where fluid rotates around an axis

Explanation:

A vortex is a flow pattern in a fluid where the flow revolves around an axis line, which may be straight or curved.

10. What is the primary application of Pascal's law in civil engineering?

a) In designing electrical circuits
b) In hydraulic systems like lifts and pumps
c) In measuring fluid temperature
d) In predicting weather patterns

Answer:

b) In hydraulic systems like lifts and pumps

Explanation:

Pascal's law, which states that pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions, is fundamental in designing hydraulic systems such as lifts and pumps.

11. What is the primary cause of cavitation in fluid systems?

a) High fluid temperature
b) High fluid viscosity
c) Rapid change in fluid pressure
d) Slow fluid velocity

Answer:

c) Rapid change in fluid pressure

Explanation:

Cavitation occurs when there is a rapid change in fluid pressure, leading to the formation of vapor bubbles in areas where the pressure of the fluid falls below its vapor pressure.

12. What does the term 'specific gravity' refer to in fluid mechanics?

a) The color intensity of a fluid
b) The weight of a fluid
c) The ratio of the density of the fluid to the density of a reference substance
d) The temperature of a fluid

Answer:

c) The ratio of the density of the fluid to the density of a reference substance

Explanation:

Specific gravity is a dimensionless quantity that describes the ratio of the density of a fluid to the density of a reference substance (usually water for liquids and air for gases).

13. What is the significance of the Darcy-Weisbach equation in fluid mechanics?

a) It is used to predict the weather
b) It calculates the electrical conductivity of a fluid
c) It determines the head loss due to friction in a pipe
d) It measures the viscosity of a fluid

Answer:

c) It determines the head loss due to friction in a pipe

Explanation:

The Darcy-Weisbach equation is used to calculate the head loss (or pressure loss) due to friction in a pipe or duct.

14. In fluid mechanics, what is the boundary layer?

a) A layer of fluid at the boundary of a solid where the fluid velocity changes
b) The outermost layer of a fluid in a container
c) A layer in the fluid where temperature changes
d) A special layer used for fluid storage

Answer:

a) A layer of fluid at the boundary of a solid where the fluid velocity changes

Explanation:

The boundary layer is a thin layer of fluid at the boundary of a solid body where the fluid velocity changes from zero at the surface (no-slip condition) to the free stream velocity.

15. What is meant by 'turbulent flow' in fluid mechanics?

a) A smooth and orderly flow
b) A chaotic and irregular flow
c) The flow in only straight pipes
d) The flow in closed containers

Answer:

b) A chaotic and irregular flow

Explanation:

Turbulent flow is characterized by chaotic and irregular fluid motion, often occurring at high velocities and involving rapid variations in pressure and flow velocity.

16. How is the flow rate of a fluid typically measured?

a) Using a thermometer
b) Using a manometer
c) Using a flowmeter
d) Using a barometer

Answer:

c) Using a flowmeter

Explanation:

The flow rate of a fluid is commonly measured using a flowmeter, a device that quantifies the amount of fluid passing through it.

17. What is the impact of fluid compressibility in fluid mechanics?

a) It affects the fluid's taste
b) It changes the fluid's color
c) It influences how fluid pressure is transmitted in systems
d) It has no impact in fluid mechanics

Answer:

c) It influences how fluid pressure is transmitted in systems

Explanation:

Fluid compressibility, the measure of the change in volume of a fluid in response to a change in pressure, significantly influences how pressure is transmitted and fluid behaves in different systems.

18. What is a manometer used for in fluid mechanics?

a) Measuring fluid velocity
b) Measuring fluid density
c) Measuring pressure differences in fluids
d) Measuring fluid viscosity

Answer:

c) Measuring pressure differences in fluids

Explanation:

A manometer is an instrument used to measure the pressure of a fluid, or the difference in pressure between two points in a fluid.

19. What does the Archimedes' principle state about fluids?

a) A body immersed in a fluid experiences a buoyant force equal to the weight of the fluid displaced
b) Fluids flow from higher to lower pressure
c) The viscosity of a fluid increases with temperature
d) The volume of a fluid remains constant under pressure

Answer:

a) A body immersed in a fluid experiences a buoyant force equal to the weight of the fluid displaced

Explanation:

Archimedes' principle states that any object, wholly or partly immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.

20. What is the primary application of the continuity equation in fluid mechanics?

a) Describing the behavior of gases only
b) Conservation of mass in a fluid flow
c) Predicting the change in fluid temperature
d) Calculating the electrical conductivity of fluids

Answer:

b) Conservation of mass in a fluid flow

Explanation:

The continuity equation in fluid mechanics is a mathematical statement of the principle of mass conservation, stating that the mass flow rate in a fluid flow system remains constant.

21. What is capillarity in fluid mechanics?

a) The study of high-pressure fluids
b) The ability of a fluid to flow in narrow spaces without external assistance
c) The change in fluid color under pressure
d) The heating of fluids in capillary tubes

Answer:

b) The ability of a fluid to flow in narrow spaces without external assistance

Explanation:

Capillarity, or capillary action, is the ability of a liquid to flow in narrow spaces without the assistance of external forces (like gravity), often against them, due to adhesive and cohesive forces of the liquid.

22. In fluid mechanics, what does the term 'streamline' represent?

a) A type of fluid
b) A visual representation of a flowing fluid's path
c) The top layer of a fluid in motion
d) A special tool for measuring velocity

Answer:

b) A visual representation of a flowing fluid's path

Explanation:

In fluid mechanics, a streamline is a line that is everywhere tangent to the velocity field of the fluid, representing the path that a fluid element will follow.

23. What is critical flow in fluid mechanics?

a) The flow under normal conditions
b) The minimum flow rate of a fluid
c) A flow condition where the flow velocity equals the wave velocity
d) The maximum possible flow rate of a fluid

Answer:

c) A flow condition where the flow velocity equals the wave velocity

Explanation:

Critical flow in fluid mechanics is a condition where the flow velocity of the fluid equals the speed of waves on the fluid's surface, often occurring at the threshold between subcritical and supercritical flow.

24. How is the Mach number relevant in fluid mechanics?

a) It measures the viscosity of a fluid
b) It is the ratio of the fluid's velocity to the speed of sound in that fluid
c) It indicates the fluid's temperature
d) It measures the fluid's density

Answer:

b) It is the ratio of the fluid's velocity to the speed of sound in that fluid

Explanation:

The Mach number in fluid mechanics is a dimensionless quantity that represents the ratio of the flow velocity past a boundary to the local speed of sound in the fluid.

25. What is the primary purpose of a pump in fluid mechanics?

a) To cool down fluids
b) To increase the pressure and transport fluids from one location to another
c) To measure the fluid’s pH level
d) To change the fluid's color

Answer:

b) To increase the pressure and transport fluids from one location to another

Explanation:

In fluid mechanics, a pump is a device used to move fluids (including liquids and gases), typically by increasing the pressure, enabling their transportation from one location to another.

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