# 1080+ Fluid Mechanics (FM) Solved MCQs

Chapters

70
26.3k
Chapter: Flow Through Pipes
1.

## The velocity corresponding to Reynold number of 2000 is called

A. Sub-sonic velocity
B. Super-sonic velocity
C. Lower critical velocity
D. Higher critical velocity
2.

A. v²/2g
B. 0.5v²/2g
C. 0.375v²/2g
D. 0.75v²/2g
3.

## Which of the following is an example of laminar flow?

A. Underground flow
B. Flow past tiny bodies
C. Flow of oil in measuring instruments
D. All of these
4.

## The discharge over a rectangular weir, considering the velocity of approach, is (whereH1 = H + Ha = Total height of water above the weir, H = Height of water over the crest of the weir, and Ha = Height of water due to velocity of approach)

A. (2/3) Cd × L.√2g [H1 - Ha]
B. (2/3) Cd × L. √2g [H13/2 - Ha3/2]
C. (2/3) Cd × L.√2g [H12 - Ha2]
D. (2/3) Cd × L. √2g [H15/2 - Ha5/2]
Answer» B. (2/3) Cd × L. √2g [H13/2 - Ha3/2]
5.

A. 50 %
B. 56.7 %
C. 66.67 %
D. 76.66 %
6.

## The efficiency of power transmission through pipe is (where H = Total supply head, and hf = Head lost due to friction in the pipe)

A. (H - hf )/H
B. H/(H - hf )
C. (H + hf )/H
D. H/(H + hf )
Answer» A. (H - hf )/H
7.

## The hydraulic mean depth or the hydraulic radius is the ratio of

A. Area of flow and wetted perimeter
B. Wetted perimeter and diameter of pipe
C. Velocity of flow and area of flow
D. None of these
Answer» A. Area of flow and wetted perimeter
8.

A. d/6
B. d/4
C. d/2
D. d
9.

## A flow in which each liquid particle has a definite path, and the paths of individual particles do not cross each other, is called

B. Uniform flow
C. Streamline flow
D. Turbulent flow
10.

## The Reynold's number of a ship is __________ to its velocity and length.

A. Directly proportional
B. Inversely proportional
C. Square root of velocity
D. None of these
11.

## The velocity at which the laminar flow stops, is known as

A. Velocity of approach
B. Lower critical velocity
C. Higher critical velocity
D. None of these
12.

## The velocity corresponding to Reynold number of 2800, is called

A. Sub-sonic velocity
B. Super-sonic velocity
C. Lower critical velocity
D. Higher critical velocity
13.

## The total energy of a liquid particle in motion is equal to

A. Pressure energy + kinetic energy + potential energy
B. Pressure energy - (kinetic energy + potential energy)
C. Potential energy - (pressure energy + kinetic energy
D. Kinetic energy - (pressure energy + potential energy)
Answer» A. Pressure energy + kinetic energy + potential energy
14.

## When a cylindrical vessel containing liquid is revolved about its vertical axis at a constant angular velocity, the pressure

A. Varies as the square of the radial distance
B. Increases linearly as its radial distance
C. Increases as the square of the radial distance
D. Decreases as the square of the radial distance
15.

A. v₁²/2g
B. v₂²/2g
C. 0.5 v₁²/2g
D. 0.375 v₂²/2g
16.

## A large Reynold number is indication of

A. Smooth and streamline flow
B. Laminar flow
D. Highly turbulent flow
17.

## A tank of uniform cross-sectional area (A) containing liquid upto height (H1) has an orifice of cross-sectional area (a) at its bottom. The time required to empty the tank completely will be

A. (2A√H₁)/(Cd × a√2g)
B. (2AH₁)/(Cd × a√2g)
C. (2AH₁3/2)/(Cd × a√2g)
D. (2AH₁²)/(Cd × a√2g)
18.

19.

## For pipes, turbulent flow occurs when Reynolds number is

A. Less than 2000
B. Between 2000 and 4000
C. More than 4000
D. Less than 4000
20.

## The discharge through a siphon spillway is

A. Cd × a × √(2gH)
B. Cd × a × √(2g) × H3/2
C. Cd × a × √(2g) × H2
D. Cd × a × √(2g) × H5/2
Answer» A. Cd × a × √(2gH)
21.

## The shear stress-strain graph for a Newtonian fluid is a

A. Straight line
B. Parabolic curve
C. Hyperbolic curve
D. Elliptical
22.

A. ω.r/2g
B. ω².r²/2g
C. ω.r/4g
D. ω².r²/4g
23.

## The region between the separation streamline and the boundary surface of the solid body is known as

A. Wake
B. Drag
C. Lift
D. Boundary layer
24.

## The total pressure on the top of a closed cylindrical vessel of radius (r) completely filled up with liquid of specific weight (w) and rotating at (ω) rad/s about its vertical axis, is

A. π w ω² r²/4g
B. π w ω² r³/4g
C. π w ω² r⁴/4g
D. π w ω² r²/2g
Answer» C. π w ω² r⁴/4g
25.

## The diameter of the nozzle (d) for maximum transmission of power is given by (where D = Diameter of pipe, f = Darcy’s coefficient of friction for pipe, and l = Length of pipe)

A. d = (D⁵/8fl)1/2
B. d = (D⁵/8fl)1/3
C. d = (D⁵/8fl)1/4
D. d = (D⁵/8fl)1/5
26.

## The fluid forces considered in the Navier Stokes equation are

A. Gravity, pressure and viscous
B. Gravity, pressure and turbulent
C. Pressure, viscous and turbulent
D. Gravity, viscous and turbulent
Answer» A. Gravity, pressure and viscous
27.

## Select the wrong statement

A. An equivalent pipe is treated as an ordinary pipe for all calculations
B. The length of an equivalent pipe is equal to that of a compound pipe
C. The discharge through an equivalent pipe is equal to that of a compound pipe
D. The diameter of an equivalent pipe is equal to that of a compound pipe
Answer» D. The diameter of an equivalent pipe is equal to that of a compound pipe
28.

29.

## The velocity at which the flow changes from laminar flow to turbulent flow is called

A. Critical velocity
B. Velocity of approach
C. Sub-sonic velocity
D. Super-sonic velocity
30.

A. flv²/2gd
B. flv²/gd
C. 3flv²/2gd
D. 4flv²/2gd
31.

A. 4μvl/wd²
B. 8μvl/wd²
C. 16μvl/wd²
D. 32μvl/wd²
32.

A. Velocity
B. (Velocity)2
C. (Velocity)3
D. (Velocity)4
33.

C. Uniform
D. Laminar
34.

## The main property that affects a boundary layer is__________

A. Temperature
B. Pressure
C. Viscosity
D. Surface tension
Explanation: A boundary layer is an important concept that refers to the layer of fluid. The fluid that is in the immediate vicinity of a bounding surface. The main property that affects a boundary layer is viscosity.
35.

## The layer that is influenced by a planetary boundary is called______

A. Atmospheric boundary layer
B. Lithosphere
C. Troposphere
D. Hydrosphere
Explanation: The planetary boundary layer is also called as atmospheric boundary layer(ABL). It is the lowest part of the atmosphere. The behaviour of ABL is directly influenced by its contact with the planetary surface.
36.

## What is the other name for Stoke’s boundary layer?

A. Momentum boundary layer
B. Atmospheric boundary layer
C. Oscillatory boundary layer
D. Thermal boundary layer
Explanation: Stoke’s boundary layer is also called as Oscillatory boundary layer. It is a boundary layer that is close to a solid wall. It moves in an oscillatory motion. It arrested by a viscous force acting in the opposite direction.
37.

## Eddy viscosity is a turbulent transfer of_________

A. Fluid
B. Heat
C. Momentum
D. Pressure
Explanation: Eddy viscosity is a turbulent transfer of momentum by eddies. It gives rise to an internal fluid friction. It is in analogous to the action of molecular viscosity in laminar fluid flow. Eddy viscosity takes place on a large scale.
38.

## The laminar boundary layer is a _________

A. Smooth flow
B. Rough flow
C. Uniform flow
D. Random flow
Explanation: For a laminar boundary layer the fluid moves in a very smooth flow. The laminar flow creates less skin friction drag. It is a less stable flow. The laminar boundary layer has got an increase in its thickness.
39.

## The turbulent boundary layer is a _________

A. Non-uniform with swirls
B. Uniform
C. Less stable
D. Smooth
Explanation: For a turbulent boundary layer the fluid moves in different direction producing swirls. It has more skin friction drag than that of laminar boundary layer. It is more stable when compared to laminar.
40.

## How do we measure the flow rate of liquid?

A. Coriolis method
C. Conveyor method
D. Ionization method
Explanation: Coriolis concept of measurement of fluid takes place through the rotation with the reference frame. It is an application of the Newton’s Law. The device continuously records, regulates and feeds large volume of bulk materials.
41.

## How does a turbulent boundary layer produce swirls?

A. Due to random motion
B. Collision of molecules
C. Due to eddies
D. Due to non-uniform cross section
Explanation: For a turbulent boundary layer the fluid moves in different direction producing swirls. It produces swirls due to the presence of eddies. The smooth laminar boundary layer flow breaks down and transforms to a turbulent flow.
42.

## Define Viscosity.

A. Resistance to flow of object
B. Resistance to flow of air
C. Resistance to flow of fluid
D. Resistance to flow of heat
Answer» C. Resistance to flow of fluid
Explanation: Viscosity is developed due to the relative motion between two surfaces of fluids at different velocities. It happens due to the shear stress developed on the surface of the fluid.
43.

## How can we determine whether the flow is laminar or turbulent?

A. Reynold’s number
B. Mach number
C. Froude number
D. Knudsen number
Explanation: Reynold’s number is used to determine whether the flow is laminar or turbulent. If Reynold’s number is less than 2000, it is a laminar flow. If Reynold’s number is greater than 2000, then it is a turbulent flow.
44.

## The flow separation occurs when the fluid travels away from the __________

A. Surface
B. Fluid body
D. Inter-molecular spaces
Explanation: Adverse pressure gradient takes place when the static pressure increases. It increases the direction of the flow. Adverse pressure gradient plays an important role in flow separation. Thus, option c is correct.
45.

## The swirl caused due to eddies are called as ______

A. Vortices
B. Vertices
C. Volume
D. Velocity
Explanation: Vortices are a region in a fluid. It takes place when the flow revolves around an axis line. Vortices can be straight or curved. They form shapes like smoke rings and whirlpools.
46.

## Which among the following is a device that converts a laminar flow into a turbulent flow?

B. Vacuum Gauge
C. Turbulator
D. Ionization Gauge
Explanation: Turbulator is a device that converts a laminar flow into a turbulent flow. The turbulent flow can be desired parts of an aircraft or also in industrial applications. Turbulator is derived from the word “turbulent”.
47.

## With the boundary layer separation, displacement thickness________

A. Increases
B. Decreases
C. Remains Same
D. Independent
Explanation: With the boundary layer separation, displacement thickness increases sharply. This helps to modify the outside potential flow and its pressure field. Thus, option ‘a’ is the correct choice.
48.

## What is the instrument used for the automatic control scheme during the fluid flow?

A. Rotameters
B. Pulley plates
C. Rotary Piston
D. Pilot Static Tube
Explanation: Pilot static tube is a system that uses an automatic control scheme to detect pressure. It has several holes connected to one side of the device. These outside holes are called as a pressure transducer, which controls the automatic scheme during fluid flow.
49.

A. Resistance= 0
B. Drag force= 0
C. Temperature = 0
Explanation: D’Alembert’s Paradox states that for an incompressible and inviscid flow potential flow, the drag force is equal to zero. The fluid is moving at a constant velocity with respect to its relative fluid.
50.

## The steady- state flow must satisfy ___________

A. Kirchhoff’s law
B. Newtons law
C. Rutherford’s experiment
D. Kepler’s law
Explanation: The steady state flow must satisfy Kirchhoff’s first and second law. The first law states that the total flow into the junction equals the total flow away from the junction. Second law is called as the law of conservation of mass. It states that between two junctions, the head loss is independent of the path followed
51.

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

A. Darcey equation
B. Poiseuille law
C. Reynolds equation
D. Sherwood 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
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
54.

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

A. density
B. specific gravity
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
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
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. 3:2
B. 9:4
C. 2:3
63.

A. 3:2
B. 9:4
C. 2:3
64.

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

A. equal to
B. half
C. twice
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
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
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
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
70.

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

A. Entry
B. Exit
C. Connection between two pipes
71.

A. Z1-Z2
B. C
C. T2-T1
72.

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

B. Subtract them
C. Multiply 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
Answer» B. Directly proportional to mass flow rate
75.

A. Re/16
B. Re/64
C. 16/Re
76.

## Shear stress in static fluid is

A. always zero
B. always maximum
C. between zero to maximum
D. unpredictable
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
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
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
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
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
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
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?

B. Subtract them
C. Multiply them
D. Divide 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
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
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
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
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
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
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
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