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1080+ Fluid Mechanics (FM) Solved MCQs

These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Civil Engineering .

Chapters

Chapter: Flow Through Pipes
51.

What is the name of the equation? Q = (πΔPr4) / (8μL)

A. Darcey equation
B. Poiseuille law
C. Reynolds equation
D. Sherwood law
Answer» B. Poiseuille law
Explanation: The Hagen–Poiseuille equation also called as the Hagen–Poiseuille law, is a physical law that gives the pressure drop in an incompressible and Newtonian fluid which is flowing through a long cylindrical pipe in laminar flow of constant cross section.
52.

What is the name of the equation? h = (fvL) / (2Dg)

A. Darcey equation
B. Poiseuille law
C. Reynolds equation
D. Sherwood law
Answer» A. Darcey equation
Explanation: It’s a constitutive equation that describes the flow of a fluid through a porous medium. It’s based on the results of experiments on the flow of H2O through beds of sand, forming the basis of hydrogeology, a branch of earth sciences.
53.

Which one of the following is a major loss?

A. frictional loss
B. shock loss
C. entry loss
D. exit loss View Answer
Answer» A. frictional loss
54.

Which property of the fluid accounts for the major losses in pipes?

A. density
B. specific gravity
C. viscosity
D. compressibility View Answer
Answer» C. viscosity
55.

The frictional resistance for fluids in motion is

A. proportional to the velocity in laminar flow and to the square of the velocity in turbulent flow
B. proportional to the square of the velocity in laminar flow and to the velocity in turbulent flow
C. proportional to the velocity in both laminar flow and turbulent flow
D. proportional to the square of the velocity in both laminar flow and turbulent flow
Answer» A. proportional to the velocity in laminar flow and to the square of the velocity in turbulent flow
56.

The frictional resistance for fluids in motion is

A. dependent on the pressure for both laminar and turbulent flows
B. independent of the pressure for both laminar and turbulent flows
C. dependent on the pressure for laminar flow and independent of the pressure for turbulent flow
D. independent of the pressure for laminar flow and dependent on the pressure for turbulent flow View Answer
Answer» B. independent of the pressure for both laminar and turbulent flows
57.

The frictional resistance for fluids in motion is

A. inversely proportional to the square of the surface area of contact
B. inversely proportional to the surface area of contact
C. proportional to the square of the surface area of contact
D. proportional to the surface area of contact
Answer» D. proportional to the surface area of contact
58.

The frictional resistance for fluids in motion varies

A. slightly with temperature for both laminar and turbulent flows
B. considerably with temperature for both laminar and turbulent flows
C. slightly with temperature for laminar flow and considerably with temperature for turbulent flow
D. considerably with temperature for laminar flow and slightly with temperature for turbulent flow View Answer
Answer» D. considerably with temperature for laminar flow and slightly with temperature for turbulent flow View Answer
59.

Which one of the follflowing is correct?

A. the frictional resistance depends on the nature of the surface area of contact
B. the frictional resistance is independent of the nature of the surface area of contact
C. the frictional resistance depends on the nature of the surface area of contact for laminar flows but is independent of the nature of the surface area of contact for turbulent flows
D. the frictional resistance is independent of the nature of the surface area of contact for laminar flows but depends on the nature of the surface area of contact for turbulent flows View Answer
Answer» D. the frictional resistance is independent of the nature of the surface area of contact for laminar flows but depends on the nature of the surface area of contact for turbulent flows View Answer
60.

Which one of the follflowing is correct?

A. the frictional resistance is always dependent on the nature of the surface area of contact
B. the frictional resistance is always independent of the nature of the surface area of contact
C. the frictional resistance is dependent on the nature of the surface area of contact when the liquid flows at a velocity less than the critical velocity
D. the frictional resistance is independent of the nature of the surface area of contact when the liquid flows at a velocity less than the critical velocity View Answer
Answer» D. the frictional resistance is independent of the nature of the surface area of contact when the liquid flows at a velocity less than the critical velocity View Answer
61.

Which one of the follflowing is correct?

A. Darcy-Weisbach’s formula is generally used for head loss in flow through both pipes and open channels
B. Chezy’s formula is generally used for head loss in flow through both pipes and open channels
C. Darcy-Weisbach’s formula is generally used for head loss in flow through both pipes and Chezy’s formula for open channels
D. Chezy’s formula is generally used for head loss in flow through both pipes and Darcy-Weisbach’s formula for open channels View Answer
Answer» C. Darcy-Weisbach’s formula is generally used for head loss in flow through both pipes and Chezy’s formula for open channels
62.

A liquid flows through pipes 1 and 2 with the same flow velocity. If the ratio of their pipe diameters d1 : d2 be 3:2, what will be the ratio of the head loss in the two pipes?

A. 3:2
B. 9:4
C. 2:3
D. 4:9 View Answer
Answer» C. 2:3
63.

A liquid flowss through two similar pipes 1 and 2. If the ratio of their flow velocities v1 : v2 be 2:3, what will be the ratio of the head loss in the two pipes?

A. 3:2
B. 9:4
C. 2:3
D. 4:9 View Answer
Answer» D. 4:9 View Answer
64.

A liquid flows with the same velocity through two pipes 1 and 2 having the same diameter. If the length of the second pipe be twice that of the first pipe, what should be the ratio of the head loss in the two pipes?

A. 1:2
B. 2:1
C. 1:4
D. 4:1
Answer» A. 1:2
65.

The head loss at the entrance of the pipe is that at it’s exit

A. equal to
B. half
C. twice
D. four times View Answer
Answer» B. half
66.

On which of the factors does the co-efficent of bend in a pipe depend?

A. angle of bend and radius of curvature of the bend
B. angle of bend and radius of the pipe
C. radius of curvature of the bend and pipe
D. radius of curvature of the bend and pipe and angle of bend View Answer
Answer» D. radius of curvature of the bend and pipe and angle of bend View Answer
Explanation: Explanation: The co-efficent of bend in a pipe depends on all the three parameters – radius of curvature of the bend, diameter (radius) of the pipe and angle of bend.
67.

The liquid flowing through a series of pipes can take up__________

A. Pipes of different diameters
B. Pipes of the same diameters only.
C. Single pipe only
D. Short pipes only View Answer
Answer» A. Pipes of different diameters
68.

What is the total loss developed in a series of pipes?

A. Sum of losses in each pipe only
B. Sum of local losses only
C. Sum of local losses plus the losses in each pipe
D. Zero View Answer
Answer» C. Sum of local losses plus the losses in each pipe
69.

The total head loss for the system is equal to_________

A. Pipe length
B. Pipe diameter
C. Width of the reservoir
D. Height difference of reservoirs View Answer
Answer» D. Height difference of reservoirs View Answer
70.

Which among the following is not a loss that is developed in the pipe?

A. Entry
B. Exit
C. Connection between two pipes
D. Liquid velocity View Answer
Answer» D. Liquid velocity View Answer
71.

Which among the following is the correct formula for head loss?

A. Z1-Z2
B. C
C. T2-T1
D. S2-S1 View Answer
Answer» A. Z1-Z2
72.

If the two reservoirs are kept at the same level, the head loss is _______

A. Z1-Z2
B. Zero
C. T2-T1
D. S2-S1
Answer» B. Zero
73.

How do we determine the total discharge through parallel pipes?

A. Add them.
B. Subtract them
C. Multiply them
D. Divide them View Answer
Answer» A. Add them.
74.

The pipe diameter is ________

A. Directly proportional to fluid density
B. Directly proportional to mass flow rate
C. Inversely proportional to mass flow rate
D. Directly proportional to fluid velocity View Answer
Answer» B. Directly proportional to mass flow rate
75.

Coefficient of friction of a laminar flow is_________

A. Re/16
B. Re/64
C. 16/Re
D. 64/Re View Answer
Answer» C. 16/Re
76.

Shear stress in static fluid is

A. always zero
B. always maximum
C. between zero to maximum
D. unpredictable
Answer» A. always zero
Explanation: ways zero
77.

The specific weight of the fluid depends upon

A. gravitational acceleration
B. mass density of the fluid
C. both a. and b.
D. none of the above
Answer» B. mass density of the fluid
Explanation: th a. and b.
78.

The rate of increase of velocity with respect to change in the position of fluid particle in a flow field is called as

A. local acceleration
B. temporal acceleration
C. convective acceleration
D. all of the above
Answer» C. convective acceleration
Explanation: vective acceleration
79.

Minor losses occur due to

A. sudden enlargement in pipe
B. sudden contraction in pipe
C. bends in pipe
D. all of the above
Answer» A. sudden enlargement in pipe
Explanation: l of the above
80.

Kinematic eddy viscosity (ε) is the ratio of

A. eddy viscosity (η) to dynamic viscosity (μ)
B. eddy viscosity (η) to kinematic viscosity (ν)
C. kinematic viscosity to eddy viscosity (η)
D. eddy viscosity (η) to mass density (ρ)
Answer» D. eddy viscosity (η) to mass density (ρ)
Explanation: y viscosity (η) to mass density (ρ)
81.

The friction factor in fluid flowing through pipe depends upon

A. Reynold’s number
B. relative roughness of pipe surface
C. both a. and b.
D. none of the above
Answer» B. relative roughness of pipe surface
Explanation: th a. and b.
82.

What is the effect of change in Reynold’s number on friction factor in turbulent flow?

A. As the Reynold’s number increases the friction factor increases in turbulent flow
B. As the Reynold’s number increases the friction factor decreases in turbulent flow
C. change in Reynold’s number does not affect the friction factor in turbulent flow
D. unpredictable
Answer» A. As the Reynold’s number increases the friction factor increases in turbulent flow
Explanation: s the Reynold’s number increases the friction factor decreases in turbulent flow
83.

The component of the total force exerted by fluid on a body in the direction parallel to the direction of motion is called as

A. lift
B. drag
C. both a. and b.
D. none of the above
Answer» A. lift
Explanation: g
84.

The sum of components of shear forces in the direction of flow of fluid is called as

A. shear drag
B. friction drag
C. skin drag
D. all of the above
Answer» A. shear drag
Explanation: l of the above
85.

The liquid flowing through a series of pipes can take up__________

A. Pipes of different diameters
B. Pipes of the same diameters only.
C. Single pipe only
D. Short pipes only
Answer» A. Pipes of different diameters
Explanation: When pipes of different diameters are connected at its ends to form a pipe, this pipe so developed is called as pipes in series. They might not have to be of the same diameters. But, having the same diameters are better as it avoids the losses so developed.
86.

What is the total loss developed in a series of pipes?

A. Sum of losses in each pipe only
B. Sum of local losses only
C. Sum of local losses plus the losses in each pipe
D. Zero
Answer» C. Sum of local losses plus the losses in each pipe
Explanation: When the pipes of different diameters are connected in series from end to end to form a pipe line. The total loss so developed is equal to the sum of local losses plus the losses in each pipe. The local losses are developed at the connection point.
87.

The total head loss for the system is equal to_________

A. Pipe length
B. Pipe diameter
C. Width of the reservoir
D. Height difference of reservoirs
Answer» D. Height difference of reservoirs
Explanation: Total head loss for a system is equal to the height difference of the reservoirs. Height difference is denoted by the letter ‘H’. Total head loss can be equated by summing it up with all the local losses and the losses at each pipe.
88.

Which among the following is not a loss that is developed in the pipe?

A. Entry
B. Exit
C. Connection between two pipes
D. Liquid velocity
Answer» D. Liquid velocity
Explanation: Liquid velocity in the pipe is the velocity with which the liquid travels through different cross sections of the pipe. It is a vector field which is used to describe the motion of a continuum. The length of flow velocity vector is equal to the flow speed.
89.

Which among the following is the correct formula for head loss?

A. Z1-Z2
B. C
C. T2-T1
D. S2-S1
Answer» A. Z1-Z2
Explanation: Total head loss for a system is equal to the height difference of the reservoirs. Height difference is denoted by the letter ‘H’. Total head loss can be equated by summing it up with all the local losses and the losses at each pipe. Here, the height difference between the reservoirs is Z1-Z2.
90.

If the two reservoirs are kept at the same level, the head loss is _______

A. Z1-Z2
B. Zero
C. T2-T1
D. S2-S1
Answer» B. Zero
Explanation: Total head loss for a system is equal to the height difference of the reservoirs. Height difference is denoted by the letter ‘H’. The height difference between the reservoirs is Z1-Z2. Since they are of the same level, Z1=Z2. Therefore, head loss is zero.
91.

How do we determine the total discharge through parallel pipes?

A. Add them.
B. Subtract them
C. Multiply them
D. Divide them
Answer» A. Add them.
Explanation: Total discharge in parallel pipes are determined by adding the discharges so developed in individual pipes. If Q1 is the discharge through pipe 1 and Q2 is the discharge through pipe 2. Then the total discharge through parallel pipes is equal to Q1+Q2.
92.

The pipe diameter is ________

A. Directly proportional to fluid density
B. Directly proportional to mass flow rate
C. Inversely proportional to mass flow rate
D. Directly proportional to fluid velocity
Answer» B. Directly proportional to mass flow rate
Explanation: The pipe diameter is directly proportional to mass flow rate of fluid. Pipe diameter can be calculated if volumetric flow rate and velocity are known. ‘D’ is inversely proportional to its velocity.
93.

Coefficient of friction of a laminar flow is_________

A. Re/16
B. Re/64
C. 16/Re
D. 64/Re
Answer» C. 16/Re
Explanation: Coefficient of friction is defined as the value that shows relationship between force and the normal reaction. It is mainly used to find out an object’s normal force and frictional force. Thus, it is equal to 16/Re
94.

Which among the following force is developed due to resistance of a fluid flow?

A. Viscous force
B. Inertial force
C. Gravity force
D. Pressure force
Answer» A. Viscous force
Explanation: Viscous force is the force that is developed due to resistance of a fluid flow. Viscous force is equal to the product of shear stress due to viscosity and surface area of the fluid. It acts in the opposite direction to that of the acceleration.
95.

Which among the following force is developed due to resistance in its state of motion?

A. Viscous force
B. Inertial force
C. Gravity force
D. Pressure force
Answer» B. Inertial force
Explanation: Inertial force is the force that has resistance to any physical object that undergoes a change in its state of motion. Inertial force is the product acceleration of fluid and its mass. It acts opposite to the direction of acceleration.
96.

Which among the following is the correct formula for gravitational force?

A. F= Gm1m2/r2
B. F= Gm1m2
C. F= m1m2/r2
D. F= Gm1m2/r3
Answer» A. F= Gm1m2/r2
Explanation: Gravitational force was derived by Newton’s theory of gravitation. It is defined as the product of mass and acceleration due to gravity of the fluid flow. It is mainly present in cases of open surface fluid flow.
97.

Which among the following is present in pipe flow?

A. Viscous force
B. Inertial force
C. Gravity force
D. Pressure force
Answer» D. Pressure force
Explanation: Pressure is a force that is applied perpendicular to the surface of an object over a unit area of force. It is defined as the product of pressure intensity and cross-sectional area of the flowing fluid. Pressure force is present in case of pipe flow.
98.

A force that is caused due to attraction of particles in the layer of fluid bulk is called?

A. Viscous force
B. Inertial force
C. Surface tension force
D. Pressure force
Answer» C. Surface tension force
Explanation: Surface tension is caused due to the attraction of particles in the surface layer of the fluid in bulk quantities. Surface tension force is defined as the product of surface tension and length of flowing fluid.
99.

A force that is needed to bring back the body to its original position is called as?

A. Viscous force
B. Elastic force
C. Gravity force
D. Pressure force
Answer» C. Gravity force
Explanation: Elastic force is the force that brings a body back to its original position. It is defined as the product of elastic stress and the area of the flowing fluid.
100.

The drag force acts in _____ to the flow velocity.

A. Perpendicular direction
B. Same direction
C. Opposite direction
D. Different directions
Answer» C. Opposite direction

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