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## Aptitude Series

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First Attempt!

**1. Which one is in a state of failure?**

a) Solid

b) Liquid

c) Gas

d) Fluid

Answer: d

Explanation: A fluid is a Tresca material with zero cohesion. In simple words, fluid is in a state of failure.

**2. A small shear force is applied on an element and then removed. If the element regains it’s original position, what kind of an element can it be?**

a) Solid

b) Liquid

c) Fluid

d) Gaseous

Answer: a

Explanation: Fluids (liquids and gases) cannot resist even a small shear force and gets permanently deformed. Hence, the element must be a solid element.

**3. In which type of matter, one won’t find a free surface?**

a) Solid

b) Liquid

c) Gas

d) Fluid

Answer: c

Explanation: Solid molecules have a definite shape due to large inter-molecular forces. In liquids, molecules are free to move inside the whole mass but rarely escape from itself. Thus, liquids can form free surfaces under the effect of gravity. But, in case of gases, molecules tend to escape due to low forces of attraction. Thus, gases won’t form any free surface.

**4. If a person studies about a fluid which is at rest, what will you call his domain of study?**

a) Fluid Mechanics

b) Fluid Statics

c) Fluid Kinematics

d) Fluid Dynamics

Answer: b

Explanation: Fluid Mechanics deals with the study of fluid at rest or in motion with or without the consideration of forces, Fluid Statics is the study of fluid at rest, Fluid Kinematics is the study of fluid in motion without consideration of forces and Fluid Dynamics is the study of fluid in motion considering the application forces.

**5. The value of the compressibility of an ideal fluid is**

a) zero

b) unity

c) infinity

d) more than that of a real fluid

Answer: a

Explanation: Ideal fluids are incompressible which means they will have zero compressibility.

**6. The value of the Bulk Modulus of an ideal fluid is**

a) zero

b) unity

c) infinity

d) less than that of a real fluid

Answer: c

Explanation: Bulk modulus k is the reciprocal of compressibility fi.

k = 1⁄fi

Ideal fluids are incompressible which means fi = 0. Thus, k will be infinity.

**7. The value of the viscosity of an ideal fluid is**

a) zero

b) unity

c) infinity

d) more than that of a real fluid

Answer: a

Explanation: Ideal fluids are non-viscous which means they will have zero viscosity.

**8. The value of the surface tension of an ideal fluid is**

a) zero

b) unity

c) infinity

d) more than that of a real fluid

Answer: a

Explanation: Ideal fluids haze zero surface tension but real fluids have some finite value of surface tension.

**9. By what factor will the hydrostatic force on one of the vertical sides of a beaker decrease if the height of the liquid column is halved?**

a) 1 ⁄ 2

b) 1 ⁄ 3

c) 1 ⁄ 4

d) 2 ⁄ 3

Answer: c

Explanation: Hydrostatic force per unit width on a vertical side of a beaker = 1 ⁄ 2 * ρgh2, where ρ = density of the liquid and h= height of liquid column. Thus, if the liquid column is halved, the hydrostatic force on the vertical face will become one-fourth.

**10. Equal volume of two liquids of densities ρ1 and ρ2 are poured into two identical cuboidal beakers. The hydrostatic forces on the respective vertical face of the beakers are F1 and F2 respectively. If ρ1 > ρ2, which one will be the correct relation between F1 and F2?**

a) F1 > F2

b) F1 ≥ F2

c) F1 < F2

d) F1 ≤ F2

Answer: a

Explanation: Hydrostatic force per unit width on a vertical side of a beaker = 1 ⁄ 2 * ρgh2, where ρ = density of the liquid and h= height of liquid column. Thus if ρ1 > ρ2, F1 > F2 and F1 ≠ F2, when the h is constant.

**11. A cubic tank is completely filled with water. What will be the ratio of the hydrostatic force exerted on the base and on any one of the vertical sides?**

a) 1:1

b) 2:1

c) 1:2

d) 3:2

Answer: b

Explanation: Hydrostatic force per unit width on a vertical side of a beaker Fv = 1 ⁄ 2 * ρgh2, where ρ = density of the liquid and h= height of the liquid column. Hydrostatic force per unit width on the base of the beaker = Fb = ρgh * h = ρgh2. Thus, Fb : Fv = 2 : 1.

**12. A rectangular lamina of width b and depth d is submerged vertically in water, such that the upper edge of the lamina is at a depth h from the free surface. What will be the expression for the depth of the centroid (G)?**

a) h

b) h + d

c) h + d ⁄ 2

d) h + d / 2

Answer: c

Explanation: The centroid of the lamina will be located at it’s centre. ( d ⁄ 2). Thus, the depth of the centre of pressure will be h + d ⁄ 2.

**13. A Hydraulic press has a ram of 30 cm diameter and a plunger of of 2 cm diameter. It is used for lifting a weight of 35 kN. Find the force required at the plunger.**

a) 233.3 kN

b) 311.1 kN

c) 466.6 kN

d) 155.5 kN

Answer: d

Explanation: F/a=W/A

F=(35000*3.142*.02*.02)/(3.142*0.3*0.3)

=155.5 kN.

**14. The pressure at a point in the fluid is 4.9 N/cm2. Find height when the fluid under consideration is in oil of specific gravity of 0.85.**

a) 5.83 m

b) 11.66 m

c) 17.49 m

d) 8.74 m

Answer: a

Explanation: Height=p/ρg

=48620/850*9.81

=5.83 m.

**15. An open tank contains water upto a depth of 350 cm and above it an oil of specific gravity 0.65 for a depth of 2.5 m. Find the pressure intensity at the extreme bottom of the tank.**

a) 5.027 N/cm2

b) 10.05 N/cm2

c) 2.51 N/cm2

d) None of the mentioned

Answer: a

Explanation: p= (specific gravity of water* height of water + specific gravity of oil* height of oil) * 9.81

= 5.027 N/cm2.

**16. The diameters of a small piston and a large piston of a hydraulic jack are 45 mm and 100 mm respectively.Force of 0.09 kN applied on smaller in size piston. Find load lifted by piston if smaller in size piston is 40 cm above the large piston. The density of fluid is 850 kg/m3**

a) 60 N/cm2

b) 12 N/cm2

c) 30 N/cm2

d) None of the mentioned

Answer: a

Explanation: Pressure at bottom of tank =ρgh + F/a

=850*9.81*0.4 + 90/3.142*0.045*0.045

=60 N/cm2.

**17. If fluid is at rest in a container of a narrow mouth at a certain column height and same fluid is at rest at same column height in a container having broad mouth, will the pressure be different at certain depth from fluid surface.**

a) Pressure will be same for both.

b) Pressure will be more for narrower mouth

c) Pressure will be less for narrower mouth

d) None of the mentioned

Answer: a

Explanation: As per hydrostatic law, the pressure depends only on the height of water column and not its shape.

**18. We can draw Mohr’s circle for a fluid at rest.**

a) True

b) false

Answer: b

Explanation: Mohr’s circle is used to denote shear stress distribution. For fluid at rest, there is no shear stress. Hence, we cannot draw Mohr’s circle for fluid at rest.

**19. Pressure intensity or force due to pressure gradient for fluid at rest is considered as which kind of force?**

a) Surface force

b) Body force

c) Force due to motion

d) None of the mentioned

Answer: a

Explanation: Pressure force is surface force.

**21. Calculate the hydrostatic pressure for water moving with constant velocity at a depth of 5 m from the surface.**

a) 49 kN/m2

b) 98 kN/m2

c) since fluid is in motion, we cannot analyse

d) None of the mentioned

Answer: a

Explanation: If fluid is moving with uniform velocity we treat it analytically same as if fluid is at rest

p= ρgh.

**22. Pressure distribution for fluid at rest takes into consideration pressure due to viscous force.**

a) True

b) False

Answer: b

Explanation: Viscous force term in pressure expression for fluid at rest is absent as their is no motion of liquid.

**23. Barometer uses the principle of fluid at rest or pressure gradient for its pressure calculation.**

a) True

b) False

Answer: a

Explanation: Principle of Barometer is Hydrostatic law.

**24. Find the position of centre of buoyancy for a wooden block of width 3.5 m and depth 1 m, when it floats horizontally in water. The density of wooden block id 850 kg/m3 and its length 7.0 m.**

a) 0.95

b) 0.85

c) 1.05

d) 1.65

Answer: b

Explanation: Weight of the block=ρ*g*Volume=850*9.81*7*3.5*1=204.29 kN

Volume of

water displaced= Weight of water displaced/weight density of water

= 20.825 m3.

h=20.825/3.5*7=0.85 m.

**25. A stone weighs 450 N in air and 200 N in water. Compute the volume of stone.**

a) .025 m3

b) .05 m3

c) .075 m3

d) None of the mentioned

Answer: a

Explanation: Weight of water displaced=Weight of stone in air – Weight of stone in water

=250

Volume of water displaced=Volume of stone=250/9.81*1000=0.025 m3.

**26. A stone weighs 650 N in air and 275 N in water. Compute its specific gravity.**

a) 1.73

b) 2.45

c) 3.46

d) 0.865

Answer: a

Explanation: Weight of water displaced=Weight of stone in air – Weight of stone in water

=375

Volume of water displaced=Volume of stone=375/9.81*1000=0.038 m3

Density of stone= mass/volume=650/9.81*0.038=1733 kg/m3

specific gravity= Density of stone/Density of water=1.73.

**27. A body of dimensions 2.7 m * 3.8 m * 2.5 m, weighs 2500 N in water.Find its weight in air.**

a) 254.12 kN

b) 508.25 kN

c) 101.65 kN

d) 127.06 kN

Answer: a

Explanation: Weight of stone in air = Weight of water displaced+Weight of stone in water

= 9.81*1000*2.7*3.8*2.5+2500=254.12 kN.

**28. Find the density of metallic body which floats at the interface of mercury of sp.gr 13.6 and water such that 40 % of its volume is sub-merged in mercury and 60% in water.**

a) 6040 kg/m3

b) 12080 kg/m3

c) 24160 kg/m3

d) 3020 kg/m3

Answer: a

Explanation: Total Bouyant force=Force of bouyancy due to water+Force of bouyancy due to mercury

For equilibrium, Total bouyant force= Weiht of body

1000*9.81*0.6*V + 13.6*1000*9.81*0.4*V=ρ*g*V

ρ=6040 kg/m3.

**29. What is the principal cause of action of buoyant force on a body submerged partially or fully in fluid?**

a) Displacement of fluid due to submerged body

b) Development of force due to dynamic action

c) Internal shear forces mitigating external forces

d) None of the mentioned

Answer: a

Explanation: The principal cause of action of buoyant force on a body submerged partially or fully in fluid is the force equal in magnitude to the weight of the volume of displaced fluid.

**30. How can relatively denser object be made to float on the less dense fluid?**

a) By altering the shape.

b) By altering the forces acting on the object

c) By altering the shear forces acting on the object

d) None of the mentioned

Answer: a

Explanation: By changing the shape of an object it can be made to float on a fluid even if it is denser than that fluid. This principle is used in ship building.

**30. What happens to the buoyant force acting on the airship as it rises in the air?**

a) Buoyant force increases

b) Buoyant force decreases

c) Buoyant force remains constant

d) Buoyant force first increases then shows decrease

Answer: b

Explanation: Buoyant force acting on the airship decreases as it rises in the air as air at higher altitude becomes rarer and its density decreases.

**31. As a balloon rises in the air its volume increases, at the end it acquires a stable height and cannot rise any further.**

a) True

b) False

Answer: a

Explanation: As balloon rises in air, pressure acting on it reduces and therefore its volume increases. Also, a rising balloon ceases rising when it and the displaced air are equal in weight.

**32. Submarines use principle of ‘neutral buoyancy’ to go into the water.**

a) True

b) False

Answer: a

Explanation: To dive, the submarine tanks are opened to allow air to exhaust, while the water flows in. When the weight has been balanced so the overall density of the submarine is equal to the water around it, it has neutral buoyancy and hence will go down.

**1. What type of flow can be taken for granted in a pipe of a uniform cross-section?**

a) steady

b) unsteady

c) uniform

d) non-uniform

Answer: c

Explanation: According to the continuity equation, ρAV =constant, where ρ= density, A= cross-sectional area of flow, V = velocity of flow. For a pipe of a uniform cross-section, no matter what the rate of flow is, the velocity of flow inside the pipe will always remain constant. Hence, it’ll always be a uniform flow. It’ll be a steady flow if and only if the water level is maintained at a constant level by supplying water at the same rate as it gets discharged, else the water level will keep decreasing with time leading to an unsteady flow.

**2. Can the flow inside a nozzle be steady and uniform?**

a) yes

b) never

c) it can be steady but never uniform

d) it can be uniform but never steady

Answer: c

Explanation: According to the continuity equation, ρAV =constant, where ρ= density, A= cross-sectional area of flow, V = velocity of flow. For a nozzle, the area gradually decreases towards it’s exit. Thus, no matter what the rate of flow is, the velocity of flow at the nozzle exit will always be greater than that at it’s entrance. Hence, it’ll always be an unsteady flow. It can be a steady flow if and only if the water level is maintained at a constant level by supplying water at the same rate as it gets discharged, else the water level will keep decreasing with time leading to an unsteady flow.

**3. Which of the following statements is true regarding one and two-dimensional flows?**

a) Flow in a pipe is always taken as one-dimensional flow

b) Flow in a pipe is always taken as two-dimensional flow

c) Flow in a pipe is taken as one-dimensional flow when average flow parameters are considered

d) Flow in a pipe is taken as two-dimensional flow when average flow parameters are considered

Answer: c

Explanation: The flow inside a pipe can be described by the cylindrical co-ordinate system (r; θ; z), where r is in the radial direction, θ in the angular direction and z in the axial direction. For a circular cross-sections, the flow can be taken to be independent of θ. Hence, it can be taken aa a two-dimensional flow. Again if aerage flow parameters are considered to account for the variation in the radial direction, the flow can be taken as an one-dimensional flow.

**4. Which of the following is true?**

a) Flow is rotational inside the boundary layer and irrotational outside

b) Flow is irrotational inside the boundary layer and rotational outside

c) Flow is rotational both inside and outside of the boundary layer

d) Flow is irrotational both inside and outside of the boundary layer

Answer: a

Explanation: When a torque is applied to a fluid particle, it undergoes a rotation. Thus, the rotation of a fluid particle will alwayds be associated with shear stress. Shear stress is in turn dependent on the viscosity. Hence, rotational flow occurs where the viscosity effects are predominant. Since, viscosity effects are predominant inside the blundary layer, the flow will be rotational in this region. However, outside the boundary layer, the viscosity effects are negligible. Hence, flow can be treated as irrotational outside the boundary layer.

**5. Which of the following is true?**

a) Flow is laminar inside the boundary layer and turbulent outside

b) Flow is turbulent inside the boundary layer and laminar outside

c) Flow is laminar both inside and outside of the boundary layer

d) Flow is turbulent both inside and outside of the boundary layer

Answer: a

Explanation: Flows can be characterized as laminar or turbulent on the basis of Reynold’s number Re = ρvd / μ, where ρ is the density, d is the pipe diameter and μ is the viscosity. For Re < 2000, the flow will be laminar and Re > 4000, the ow will be turbulent. For laminar flow, the viscosity effects must be high (μ should be high) as inside the boundary layer. Outside the boundary layer, the viscosity effects are negligible. Hence, the flow will be turbulent.

**6. “The velocity of entrance and exit through a nozzle remains the same.” Is this ever possible?**

a) only if the flow is compressible

b) only if the flow is laminar

c) only if the flow is rotational

d) never possible

Answer: a

Explanation: According to the continuity equation, ρAV =constant, where ρ= density, A= cross sectional area of flow, V = velocity of flow. If v =constant, ρA =constant. Thus a change is A will mean a change in ρ. Hence, the flow is possible only if the fluid is compressible.

**7. What will be the shape of the pathline for an one-dimensional flow be like?**

a) straight line

b) parabolic

c) hyperbolic

d) elliptical

Answer: a

Explanation: A pathline is the path followed by a particle in motion. For an one-dimensional flow, the fluids move in only one dimension (say x). Hence the pathline will also be a straight line (along that direction).

**8. Which of the following is correct?**

a) Pathlines of two particles in an one-dimensional flow can never intersect

b) Pathlines of two particles in an one-dimensional flow can never intersect if the two particles move along the same direction

c) Pathlines of two particles in an one-dimensional flow can intersect only if the two particles move along the same direction

d) Pathlines of two particles in an one-dimensional flow can intersect only if the two particles move along different directions

Answer: c

Explanation: The pathline of a particle in an one-dimensional flow is a straight line along the direction it moves. If the two particles move along the same direction, their pathlines will be parallel to each other and will never intersect.

**9. What is the maximum number of times the pathlines of two particles can intersect in an one dimensional flow?**

a) 0

b) 1

c) 2

d) infinite

Answer: b

Explanation: The pathline of a particle in an one-dimensional flow is a straight line along the direction it moves. When two particles move in the same direction, their pathline will never intersect and when they move in different directions, their pathlines will intersect only once.

**10. The velocity of a point in a flow is**

a) along the streamline

b) tangent to the streamline

c) along the pathline

d) tangent to the pathline

Answer: b

Explanation: A pathline is the path followed by a particle in motion whereas a streamline is an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point.

**11. Which of the following is correct?**

a) A streamline can intersect itself and two streamlines can cross

b) A streamline cannot intersect itself but two streamlines can cross

c) A streamline can intersect itself but two streamlines cannot cross

d) A streamline cannot intersect itself and two streamlines cannot cross

Answer: d

Explanation: A streamline is defined as an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. At a point, there can only be one direction of velocity. Hence, neither can a streamline intersect itself nor can two streamlines cross each other.

**12. The streamlines of the particles in a flow are recorded. If the streamline distribution remain the same even after sometime, what type of flow can it be?**

a) steady

b) unsteady

c) uniform

d) non-uniform

Answer: a

Explanation: A streamline is defined as an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. In a steady flow, the velocity of the particles is constant with time. Hence, the streamlines remain the same even after sometime.

**13. If the streamlines of the particles in a flow are parallel to each other, what type of flow can it be?**

a) steady

b) unsteady

c) uniform

d) non-uniform

Answer: c

Explanation: Streamline spacing varies inversely as the velocity. In a uniform flow, the velocities of the particles are the same at every instant of time. Hence, the spacing between their streamlines will be the same. In other words, the streamlines will be parallel.

**14. Which of the following is correct?**

a) the movement of fluid mass can either be along the streamlines or across them

b) the movement of fluid mass can be along the streamlines but never across them

c) the movement of fluid mass can never be along the streamlines but can be across them

d) the movement of fluid mass can neither be along the streamlines or across them

Answer: b

Explanation: A streamline is defined as an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. Flow can only be along the velocity, never perpendicular to it. Hence, the movement of fluid mass can only be along the streamlines and never across them.

**15. Which of the following is correct?**

a) pathlines are concerned with a number of particles at the same instant and streamlines with a particular particle at successive instants of time

b) pathlines are concerned with a particular particle at successive instants of time and streamlines with a number of particles at the same instant

c) both pathlines and streamlines are concerned with a number of particles at the same instant

d) both pathlines and streamlines are concerned with a particular particle at successive instants of time

Answer: b

Explanation: A pathline is the path followed by a particle in motion whereas a streamline is an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. Thus, pathlines are concerned with a particular particle at successive instants of time and streamlines with a number of particles at the same instant.

**16. In which method of fluid flow analysis do we describe the motion parameters at a point?**

a) Langragian method

b) Eulerian Method

c) Control volume analysis

d) None of the mentioned

Answer: b

Explanation: In Eulerian method,we describe velocity, acceleration pressure etc at a point in flow field.

**17. Which method is most commonly used in fluid mechanics for analysis?**

a) Langragian method

b) Eulerian Method

c) Control volume analysis

d) None of the mentioned

Answer: b

Explanation: In Eulerian method,we describe velocity, acceleration pressure etc at a point in flow field.hence, it is also most commonly used in fluid mechanics.

**18.In unsteady flow, the flow parameters change with respect to position.**

a) True

b) False

Answer: b

Explanation: In unsteady flow, the flow parameters change with respect to time.

**19. Uniform flow is defined as the type of flow in which acceleration is zero i.e velocity is constant.**

a) True

b) False

Answer: b

Explanation: Uniform flow is defined as the type of flow in which the velocity does not change with respect to space. It can change with respect to time.

**20. In laminar flow fluid particles flow along a streamline.**

a) True

b) False

Answer: a

Explanation: As per the definition of laminar flow, fluid particles flow in a streamlined manner.

**21. Eddies formed in the turbulent flow are major cause of the energy loss in the turbulent flow.**

a) True

b) False

Answer: a

Explanation: Due to zig zag motion of particles eddies are formed and they lead to energy losses.

**22. The continuity equation is based on the premise of-**

a) Law of conservation of energy

b) Law of conservation of mass

c) Law of conservation of momentum

d) None of the mentioned

Answer: b

Explanation: Continuity equation is based on the the principle of conservation of mass.

**23. The continuity equation is only applicable to incompressible fluid.**

a) True

b) False

Answer: b

Explanation: The continuity equation is only applicable to incompressible as well as compressible fluid.

**24. For incompressible fluid flow, if area reduces then what is the effect on the velocity.**

a) increases

b) decreases

c) first increases then decreases

d) first decreases then increases

Answer: a

Explanation: According to continuity equation,

Area × velocity = constant

Hence, as area decreases velocity increases.

**25. For compressible fluid flow in a pipe, having decrease in specific gravity what will be the effect of decrease in diameter?**

a) It will cause increase in velocity

b) It will cause decrease in velocity

c) It remains constant

d) None of the mentioned

Answer: a

Explanation: According to continuity equation,

ρ*A*v = constant

Hence, as density and area decreases velocity is bound to increase.

**26. What is the most common assumption while dealing with fluid flow problems using continuity equation?**

a) Flow is assumed to be compressible

b) Flow is assumed to be unsteady

c) Flow is assumed to be steady

d) Flow is assumed to be turbulent

Answer: c

Explanation: In majority of the fluid flow problems, flow is assumed to be steady.

**27. The diameters of a pipe at the sections 1 and 2 are 8 cm and 13 cm respectively. Find the discharge through pipe if the velocity of water flowing through the pipe at section 1 is 6 m/s. Determine also the velocity at section 2.**

a) 2.27 m/s

b) 4.54 m/s

c) 1.13 m/s

d) 3.25 m/s

Answer: a

Explanation: According to continuity equation,

Area × velocity = constant

Area1*Velocity1 = Area2*Velocity2

Velocity2=(Area1*Velocity1)/Area2

= (82 * 6) / 132=2.27 m/s.

**28. The continuity equation can only be used for analysis of conserved quantity.**

a) True

b) False

Answer: a

Explanation: Continuity equation is defined on a control volume and hence, is applicable only to Conserved quantities.

**29. The diameter of a pipe at the section 1 is 9 cm. If the velocity of water flowing through the pipe at section 1 is 4.8 m/s and section 2 is 9 m/s, Determine the area at section 2.**

a) 33.93 m2

b) 67.86 m2

c) 16.96 m2

d) 38.66 m2

Answer: a

Explanation: According to continuity equation,

Area × velocity = constant

Area1*Velocity1 = Area2*Velocity2

(Area1*Velocity1)/Velocity2=Area2

Area 2= 33.93 m2.

**30. Convective acceleration cannot be found if the fluid flow equation is not satisfying**

**the continuity equation but local acceleration can be found.**

a) True

b) False

Answer: b

Explanation: Convective acceleration and local acceleration cannot be found if the fluid flow equation is not satisfying the continuity equation.

**31. Local acceleration has constant value for a steady flow.**

a) True

b) False

Answer: b

Explanation: Local acceleration is zero for a steady flow.

**32. Total acceleration has the same value as convective acceleration in case of unsteady flow.**

a) True

b) False

Answer: b

Explanation: Total acceleration has the same value as convective acceleration in case of steady flow as local acceleration value becomes zero.

**33. Which equation must be perfunctorily satisfied while dealing with fluid flow problems?**

a) Newton’s second law

b) Newton’s third law

c) Law of conservation of momentum

d) Continuity equation

Answer: d

Explanation: Continuity equation must be perfunctorily satisfied while dealing with fluid flow problems.

**34. Convective acceleration is defined as the rate of change of velocity due to change of velocity with respect to time.**

a) True

b) False

Answer: b

Explanation: Convective acceleration is defined as the rate of change of velocity due to change of position of fluid particles.

**35. When fluid element moves from one position to another, what type of motion is it?**

a) Linear Translation

b) Linear Deformation

c) Angular Deformation

d) Rotation

Answer: a

Explanation: As per the definition, bodily movement of fluid element is translation.

**35. When fluid element moves from one position to another and it undergoes c hange in its dimensions, what type of motion is it?**

a) Linear Translation

b) Linear Deformation

c) Angular Deformation

d) Rotation

Answer: b

Explanation: As per the definition, bodily movement of fluid element causing it to change its dimension is linear deformation.

**36. If there is change in angle contained by two sides. the average of the angle is**

a) Linear Translation

b) Linear Deformation

c) Angular Deformation

d) Rotation

Answer: c

Explanation: As per the definition, the sum average of two angles is magnitude of angular deformation.

**37. What is the magnitude of vorticity?**

a) Twice of angular rotation

b) Thrice of angular rotation

c) Two and half times of angular rotation

d) Same as angular rotation

Answer: a

Explanation: It is the mathematical relation between the two.

**38. The flow of fluid along curvilinear or curved path is known as**

a) Curvilinear Flow

b) Circular Flow

c) Sink Flow

d) Vortex Flow

Answer: d

Explanation: The flow of fluid along curvilinear or curved path is known as Vortex flow.

**39. When external torque is absent the type of vortex flow is**

a) Circular vortex flow

b) Independent vortex flow

c) Free vortex flow

d) None of the mentioned

Answer: c

Explanation: Free vortex flow is due to the absence of any external force.

**40. Which of the following is not an example of forced vortex flow?**

a) Liquid contained in cylinder rotated about its axis

b) Flow of liquid inside impeller of a centrifugal pump

c) Flow of a water through runner of a turbine

d) Flow of the liquid around a circular bend in a pipe

Answer: d

Explanation: Flow of the liquid around a circular bend in a pipe is an example of free vortex flow.

**41. Which of the following is not an example of free vortex flow?**

a) Flow of a water through runner of a turbine

b) Flow of liquid through a hole provided at the bottom

c) A whirlpool in a river

d) Flow of the liquid around a circular bend in a pipe

Answer: a

Explanation: Flow of a water through runner of a turbine is an example of forced vortex flow.

**1. Which of the following is NOT a type of force considered in the Navier-Stokes equation?**

a) Gravity force

b) Pressure force

c) Surface tension force

d) Viscous force

Answer: c

Explanation: Gravity, Pressure force and viscous forces together constitute the derivation of the Navier-Stokes equation. Though surface tension force act on a fluid in motion, it is considered to be negligible for the Navier-Stokes equation.

**2. Which of the following equations is a result of momentum conservation for inviscid steady flows?**

a) Bernoulli’s equation

b) Navier-Stokes equation

c) First law of thermodynamics

d) Euler’s equation

Answer: d

Explanation: Bernoulli’s equation is an energy conservation equation which is obtained by integration of the Euler equation. Navier-Stokes equation is a force balance equation. The first law of thermodynamics is an energy conservation equation, too. Euler’s equation is a momentum equation. This equation is valid for inviscid steady flows.

**3. The Bernoulli’s equation in fluid dynamics is valid for _________**

a) Compressible flows

b) Transient flows

c) Continuous flows

d) Viscous flows

Answer: c

Explanation: To answer this equation, we need to know the assumptions used in Bernoulli’s equation. The Bernoulli’s theorem is only valid for ideal, steady, incompressible, continuous, inviscid and irrotational flows. So, out of the options, only continuous flows fit in the assumptions.

**4. A water flows through a pipe at a velocity 2 m/s. The pressure gauge reading is 2 bar. The datum head is given to be 2 m. Find the piezometric head. (Assume all Bernoulli’s assumptions, Density of water = 1000 kg/m3, g = 9.8 m/s2).**

a) 22.4 m

b) 22.6 m

c) 20.4 m

d) 20.6 m

Answer: a

Explanation: Piezometric head is the addition of pressure head and the datum head. The pressure head is given by P/ρg = 20.4 m. The datum head is 2 m, which makes it a total of 22.4 m. The velocity given is extra information.

**5. A student wishes to find the velocity of air flowing through a pipe. He has a pressure gauge which displays only the dynamic pressure. The pressure gauge reads 0.018 mm Hg. Assume density of air to be 1.225 kg/m3, find the velocity V of air (ρHg = 13600 kg/m3).**

a) 4 m/s

b) 2 m/s

c) 20 m/s

d) 40 m/s

Answer: b

Explanation: (0.018 mm Hg * 13.6 * 9.8) = 2.4 bar. Dynamic pressure is given by ρV2/2. Equating 2.4 bar with dynamic pressure gives V = 2 m/s.

**6. If compressibility force and surface tension force are neglected from the Newton’s second law of motion, which of the following equations result?**

a) Navier-Stokes equation

b) Euler’s equation

c) Bernoulli’s equation

d) Reynolds equation

Answer: d

Explanation: The Newton’s second law of motion comprises of 6 forces, namely, gravity, viscosity, pressure, turbulence, surface tension and compressibility forces. Reynolds equation comprises of 4 forces. Surface tension force and compressibility forces are neglected for finding Reynolds equation.

**7. What does a pitot tube measure? Upon which principle does a pitot tube work?**

a) Pressure, Bernoulli’s principle

b) Velocity, Bernoulli’s principle

c) Pressure, Euler’s equation

d) Velocity, Euler’s equation

Answer: a

Explanation: Even though a pitot tube may be primarily used to find velocity of a fluid, the Pitot tube measures pressure and not velocity. The Pitot tube works upon the Bernoulli’s principle as it gives us pressure heads.

**8. A point in a fluid flow where the flow has come to rest is called __________**

a) Pressure point

b) Initial point

c) Flow point

d) Stagnation point

Answer: d

Explanation: Stagnation point is a point at which a flow field of the local velocity of a fluid is equal to zero. At this point, the fluid is brought to rest by the object. When the velocity is zero, the static pressure is maximum.

**9. When a fluid is subjected to resistance, it undergoes a volumetric change due to __________**

a) Strain

b) Cohesion

c) Adhesion

d) Compressibility

Answer: d

Explanation: Compressibility is defined as a measure of relative change in volume of a fluid. In fluid mechanics, it is also called as isothermal compressibility due to increase in pressure and temperature.

**10. What does Kinematic Viscosity depend upon?**

a) Density

b) Pressure

c) Fluid level

d) Fluid Flow

Answer: a

Explanation: Kinematic viscosity is a quantity that represents dynamic viscosity of a fluid per unit density. Density is a major factor that determines the kinematic viscosity. As the temperature increases, density decreases thereby causing changes in the density of the fluid.

**11. What is the formula to find the kinematic viscosity of a fluid?**

a) Dynamic Viscosity * Temperature

b) Dynamic Viscosity / Density

c) 1/ dynamic viscosity

d) Density / Dynamic Viscosity

Answer: b

Explanation: Density is a major factor that determines the kinematic viscosity. As the temperature increases, density decreases thereby causing changes in the density of the fluid. Thus, kinematic viscosity and density are inversely proportional.

**12. A one dimensional flow is also called as __________**

a) A steady flow

b) A flow which involves zero transverse component

c) Uniform Flow

d) Zig-Zag flow

Answer: b

Explanation: One dimensional flow is a flow in which variations of velocity and pressure occur along one space coordinate only. A good example of one dimensional flow is a flow through pipe. During a flow through a pipe, the functions of velocity and pressure occur along the length of the pipe.

**13. What is the resultant upward pressure of a fluid on an immersed body called?**

a) Buoyancy

b) Metacentre

c) Upthrust

d) Reaction pressure

Answer: a

Explanation: Buoyancy has been explained by Archimedes Principle. The principle states that the force exerted is directly proportional to the pressure difference. This equivalent weight of the body immersed is equal to that of the fluid displaced.

**14. If a mass of 1000kg of liquid occupies a volume of one cubic meter, then 1 represents which among the following?**

a) Specific Density

b) Specific Weight

c) Specific Gravity

d) Specific Mass

Answer: c

Explanation: Specific Gravity is defined as the ratio of mass or density of a substance to that of the mass or density of a reference substance. But, provided that it has the same volume. It must also have a specified temperature and pressure.

**15. Navier- Stokes equation describes the motion of __________**

a) Solid substance

b) Non-viscous fluid

c) Viscous fluid

d) Gas

Answer: c

Explanation: The equation described by Navier- Stokes is for a viscous fluid. The balanced equation arises from Newton’s Second Law of fluid motion. It assumes that the stress in the fluid is equal to the sum of a diffusing viscous term and a pressure term.

**16. Froude number depends upon_________**

a) Flow velocity, external field and characteristic length

b) Flow velocity and mass

c) Mass flow rate and volume

d) Characteristic length and volume

Answer: a

Explanation: The Froude number is a dimensionless number. It is defined as the ratio of flow inertia to the external field. The Froude number is based on the speed-length ratio.

**17. Continuum mechanics is a branch of mechanics that deals with________**

a) Fluid particles

b) Discrete particles

c) Kinematics and mechanical behaviour

d) Hydrostatic Pressure

Answer: c

Explanation: Continuum mechanics is a branch that deals with the analysis of kinematics and mechanical behaviour of materials. It can be modelled as a continuous mass rather than as discrete particles.

**18. Which among the following cannot be used as an alternative term for a “solenoidal vector field”?**

a) Incompressible vector field

b) Divergence- free vector field

c) Transverse vector field

d) Continuous random field

Answer: d

Explanation: A random field comes under a stochastic process. It can take up values that are multidimensional vectors or points on some manifold. A random field is a list of random numbers whose indices are identified with a discrete set of points in space.

**19. The Navier- Stokes equation can be used in which of the following applications?**

a) Automobiles

b) Ocean Currents

c) Airplanes

d) Thermometer

Answer: b

Explanation: An ocean current is a continuous direct movement of seawater. Ocean currents are forces generated by acting upon the mean flow. Therefore, ocean currents satisfy Navier-Stokes equation as they have a primary horizontal water movement.

**20. Which among the following is not an example of magneto fluids?**

a) Plasma

b) Liquid metals

c) Salt water

d) Alcohol

Answer: d

Explanation: Alcohol is an organic compound on which a hydroxyl functional group is bounded to a saturated carbon atom. Alcohols work as an antifreeze solution at cool temperatures. Thus, it is not a magneto fluid.

**21. What is the velocity profile for Poiseuille flow?**

a) Zero

b) Constant

c) Linear

d) Quadratic

Answer: d

Explanation: The velocity profile for Poiseuille flow is zero at either side of the channel and non-zero in the middle. Therefore, Quadratic equation is the only possible option here.

**22. Which is the cheapest device for measuring flow / discharge rate.**

a) Venturimeter

b) Pitot tube

c) Orificemeter

d) None of the mentioned

Answer: c

Explanation: Orificemeter is the cheapest available device for measuring flow/discharge rate.

**23. The principle of Orificemeter is same as that of Venturimeter.**

a) True

b) False

Answer: a

Explanation: The working principle for both Orificemeter and Venturimeter is same.

**24. What is the relationship between Orificemeter diameter and pipe diameter**

a) Orificemeter diameter is 0.5 times the pipe diameter

b) Orificemeter diameter is one third times the pipe diameter

c) Orificemeter diameter is one fourth times the pipe diameter

d) Orificemeter diameter is equal to the pipe diameter

Answer: c

Explanation: None.

**25. The Orificemeter readings are more accurate than Venturimeter.**

a) True

b) False

Answer: b

Explanation: The Venturimeter readings are more accurate than Orificemeter.

**26. The Orificemeter readings are more accurate than Pitot tube readings.**

a) True

b) False

Answer: b

Explanation: The Pitot tube readings are more accurate than Orificemeter.

**27. The Orificemeter has a smooth edge hole.**

a) True

b) False

Answer: b

Explanation: The Orificemeter has a rough edge hole.

**28. A nanometre is connected to a section which is at a distance of about 4 to 6 times the pipe diameter upstream from orifice plate.**

a) True

b) False

Answer: b

Explanation: A manometre is connected to a section which is at a distance of about 1.5 to 2.0 times the pipe diameter upstream from orifice plate.

**29. When is orifice called ‘large orifice’?**

a) If the head of liquid is less than 5 times the depth of orifice

b) If the head of liquid is less than 2.5 times the depth of orifice

c) If the head of liquid is less Hence, 4 times the depth of orifice

d) If the head of liquid is less than 1.5 times the depth of orifice

Answer: a

Explanation: It is the correct parametric definition for ‘large orifice’.

**30. In case of any orifice, velocity always remains constant and hence discharge can be calculated.**

a) True

b) False

Answer: b

Explanation: In case of large orifice, velocity always remains variable and hence discharge cannot be calculated.

**31. The time taken to empty the tank is independent of Cd but depends only on the height and acceleration due to gravity.**

a) True

b) False

Answer: b

Explanation: The time taken to empty the tank is dependent on Cd as well as depends only on the height and acceleration due to gravity.

**32. The discharge rate is independent of the height difference and dependent only on the height.**

a) True

b) False

Answer: b

Explanation: The discharge rate is dependent of the height difference and dependent only on the height.

**33. In case of submerged orifice the discharge is substantially dependent on temperature of fluid**

a) True

b) False

Answer: b

Explanation: Discharge is dependent on temperature but minimally.

**1. For a fully-developed pipe flow, how does the pressure vary with the length of the pipe?**

a) Linearly

b) Parabolic

c) Exponential

d) Constant

Answer: a

Explanation: In a zero acceleration fully-developed flow in a pipe, the pressure gradually decreases linearly along the length of the pipe. Hence, the pressure variation is said to be linear.

**2. When a problem states “The velocity of the water flow in a pipe is 20 m/s”, which of the following velocities is it talking about?**

a) RMS velocity

b) Average velocity

c) Absolute velocity

d) Relative velocity

Answer: b

Explanation: In a pipe-flow, the velocity is always referred to the average velocity. There may be a case where all water particles move in the same direction with 20 m/s, then the average velocity will be equal to absolute velocity. But, this is only a special case. Hence, average velocity will always be true.

**3. Which of the factors primarily decide whether the flow in a circular pipe is laminar or turbulent?**

a) The Prandtl Number

b) The Pressure gradient along the length of the pipe

c) The dynamic viscosity coefficient

d) The Reynolds Number

Answer: d

Explanation: High Reynolds number flows (> 4000) are turbulent flows, whereas low Reynolds number flows (< 2100) are laminar flows. The viscosity coefficient is a part of the Reynolds number, but isn’t the only criteria for decision.

**4. How is Reynolds number defined as?**

a) Ratio of pressures in the inlet to the outlet of a pipe

b) The product of velocity of the flow and the diameter of the pipe, divided by the kinematic viscosity of fluid

c) The product of density of the fluid, velocity of the flow and the diameter of the pipe, divided by the dynamic viscosity of fluid

d) Ratio of inertia force to viscous force

Answer: d

Explanation: The question demands the definition and not the commonly used formula of Reynolds number. Some of them denote the formula of Reynolds number. The definition of Reynolds number is the ratio of inertia force to viscous force in a pipe flow.

**5. A circular pipe of radius 7 cm is used for water flow transmission. This pipe is moulded into another pipe with a square cross-section keeping the length same. (Ignore the thickness of the pipe). Calculate the hydraulic diameter of the moulded pipe. (Take π = 22/7).**

a) 11 cm

b) 7 cm

c) 3.5 cm

d) 22 cm

Answer: a

Explanation: The perimeter of the circular cross section and the square cross section will remain the same. Perimeter = 44 cm. Side of square = 11 cm. Hydraulic diameter DH of the pipe is given by 4A/P, where A = Area of cross section and P = wetted perimeter. In case of a square DH = side. Hence, the hydraulic diameter is 11 cm.

**6. Water flows through a circular tube with a velocity of 2 m/s. The diameter of the pipe is 14 cm. Take kinematic viscosity of water 10-6 m2/s and density of water 1000 kg/m3.**

a) 2.8*108

b) 2.8*105

c) 2800

d) 28000

Answer: b

Explanation: Reynolds number is given by VD/ν = (2*0.14)/10-6. Density given is extra information. One shouldn’t be confused by that.

**7. The Reynolds number is found out for a flow in a circular pipe. This circular pipe is moulded into a square pipe, keeping length of the pipe same. Ignore the thickness of the pipe. The Reynolds number changes by __________**

a) 57% decrease

b) 57% increase

c) 43% decrease

d) 43% increase

Answer: b

Explanation: The Reynolds number directly depends upon the hydraulic diameter of the pipe. Suppose the diameter of the pipe is D, the hydraulic diameter of square pipe is 1.57D. Hence, 57% increase.

**8. The flow through a circular pipe is laminar. Now, the fluid through the pipe is replaced with a more viscous fluid and passed through the pipe again with the same velocity. What can we say about the nature of this flow?**

a) The flow will become turbulent

b) The flow will be a transition flow

c) The flow will remain laminar

d) The Reynolds number of the earlier flow is required to answer this question

Answer: c

Explanation: A flow through a circular pipe is said to be laminar when the Reynolds number is below 2100. A more viscous fluid would have a higher velocity coefficient, thus reducing the Reynolds number further at the same conditions. Hence, the Reynolds number will be well below 2100. Flow will remain laminar.

**9. Shear stress is caused due to _______**

a) Friction

b) Temperature

c) Pressure

d) Volume

Answer: a

Explanation: Shear stress is caused due to friction between fluid particles. It is formed due to the presence of fluid viscosity. Shear stress arises from the force vector component which is parallel to the cross section.

**10. Which among the following is a formula for shear stress?**

a) τ = F*A

b) τ = F/A

c) τ = F/m

d) τ = F*m

Answer: b

Explanation: Shear stress is defined as the force acting per unit area. Shear stresses arise from shear components(forces), which are pairs of equal and opposite forces. These forces act on the opposite side of the object.

**11. Which among the following is the correct formula to find out the shear modulus(G)?**

a) E/2

b) v/2

c) E/2(1+v)

d) 2E(1+v)

Answer: c

Explanation: Shear modulus is also called as modulus of rigidity. It is defined as the ratio of shear stress to shear strain. Since Young modulus is equal to stress by strain. The most suitable option is option c. (E= Young’s Modulus, v= poison’s ratio)

**12. Which among the following is an assumption of Hagen-Poiseuille equation?**

a) Fluid is compressible

b) Fluid is uniform

c) Fluid is laminar

d) Fluid is turbulent

Answer: c

Explanation: Fluid flow is laminar as it is assumed to be incompressible and Newtonian. The flow is laminar through the pipe of constant cross section. Thus, there is no acceleration of fluid in the pipe. Therefore, Hagen-Poiseuille assumed that fluid flow is laminar.

**13. What is the unit of pressure gradient?**

a) Pa/m

b) Nm

c) Pa

d) N/m

Answer: a

Explanation: Pressure gradient is a dimensional quantity. It is expressed in units of pressure per unit length. It determines which quantity and which direction the pressure changes around a particular location.

**14. Which of the following is not a basic type of stress?**

a) Volumetric stress

b) Shear stress

c) Compressive stress

d) Tensile stress

Answer: a

Explanation: Volumetric stress is not a basic classification among the type of stresses as it describes the tendency of an object to deform in all directions. It deforms when the load acts uniformly in all directions.

**15. What type of force does a stress produce?**

a) Radial force

b) External force

c) Internal resistive force

d) Axial force

Answer: c

Explanation: According to the continuum mechanics, stress is a physical quantity that produces internal forces. For example: When a solid bar supports a weight, each particle of the bar pushes the particles immediately below it. This happens due to the internal resistive force that is developed due to the stress on the body.

**16. Hooke’s law is applicable within what limit?**

a) Fracture point

b) Elastic limit

c) Ultimate strength

d) Plastic limit

Answer: b

Explanation: Hooke’s law states that force is directly proportional to its extension. Hooke’s law is applicable within the elastic limit, when the body is deformed. Example: plucking the strings of a guitar.

**18. During which case will the power loss be maximum?**

a) High viscosity oil

b) Low viscosity oil

c) High viscosity water

d) Low viscosity water

Answer: a

Explanation: A highly viscous oil will offer greater resistance due to which the power loss is maximum. As we know, oil has a greater density than water. Thus, oil is more viscous than water and corresponds to a higher loss of power.

**19. Angular speed of the shaft is________**

a) 2πN/1000

b) 2πN/60

c) 2π/N

d) 2N/60

Answer: b

Explanation: Angular speed is defined as the rate at which an object changes its angles. The angle can be measured in radians. Angular speed is a scalar quantity. It is measured within a given time period.

**20. Tangential speed of the shaft is______**

a) 2πN/1000

b) πDN/1000

c) πDN/60

d) 2πN/60

Answer: c

Explanation: Tangential speed is defined as the distance travelled per unit time. It is a linear speed of something that moves around a circular path. Example of tangential speed is a point on the edge of a merry-go-round. The merry-go-round travels a greater distance in one complete rotation than the point near the centre.

**21. Fluid does not offer resistance to change of__________**

a) Temperature

b) Volume

c) Pressure

d) Shape

Answer: d

Explanation: Shape is one of the most important factors for a fluid. The forces other than gravity that fall on the fluid affects the outcome. Thus, changing the shape of the fluid cannot be controlled.

**22. If a fluid does not undergo any sort of resistance by displacement. What substance is it called?**

a) Ideal fluid

b) Solid

c) Gas

d) Water

Answer: a

Explanation: An ideal fluid is a fluid that has zero viscosity. It results in a flow called as inviscid flow. In this flow there is no existence of shear force and the viscosity vanishes.

**23. Why can’t mercury wet a glass?**

a) Cohesion

b) Adhesion

c) Surface tension

d) Compressibility

Answer: c

Explanation: Surface tension is an elastic tendency of a fluid. It results due to imbalance of intermolecular attractive forces. Any molecule at the surface of the liquid experiences a net inward force. Mercury having a higher density than water, cannot wet a glass.

**1. Which one of the following is a major loss?**

a) frictional loss

b) shock loss

c) entry loss

d) exit loss

Answer: a

Explanation: The major loss for the flflow through the pipes is due to the frictional resistance between adjacent fluid layers sliding over each other. All other losses are considered to be minor losses.

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

a) density

b) specific gravity

c) viscosity

d) compressibility

Answer: c

Explanation: The major loss for the flow through the pipes is due to the frictional resistance between adjacent fluid layers sliding over each other. This resistance arises due to the presence of viscous property of the fluid.

**3. 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

Explanation: According to the laws of fluid friction, rf / v (for steady streamline flow) and rf / v2(for turbulent flow), where rf is the frictional resistance and v is the velocity of flow.

**4. 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

Answer: b

Explanation: According to the laws of fluid friction, the frictional resistance is independent of the pressure for both laminar and turbulent flows.

**5. 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

Explanation: According to the laws of fluid friction, the frictional resistance is proportional to the surface area of contact for both laminar and turbulent flows.

**6. 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

Answer: d

Explanation: According to the laws of fluid friction, the frictional resistance for fluids in motion varies considerably with temperature for laminar flow and slightly with temperature for turbulent flow.

**7. Which one of the following 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

Answer: d

Explanation: According to the laws of fluid friction, 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.

**8. Which of the following is true?**

a) EGL always drops in the direction of c

b) EGL always rises in the direction of flow

c) EGL always remains constant in the direction of flow

d) EGL may or may not in the direction of flow

Answer: a

Explanation: EGL is obtained by plotting total head at various points along the axis of the pipe. Since the total head decreases in the direction of flow, EGL will always drop in that direction.

**9. Which of the following is true?**

a) HGL always drops in the direction of flow

b) HGL always rises in the direction of flow

c) HGL always remains constant in the direction of flow

d) HGL may or may not in the direction of flow

Answer: d

Explanation: HGL is obtained by plotting piezometric head at various points along the axis of the pipe. Since pressure may either rise or fall in the direction of flow, HGL may or may not change in that direction.

**10. The slope of HGL will be**

a) greater than that of EGL for a pipe of uniform cross-section

b) smaller than that of EGL for a pipe of uniform cross-section

c) equal than that of EGL for a pipe of uniform cross-section

d) independent of that of EGL for a pipe of uniform cross-section

Answer: c

Explanation: The vertical intercept between EGL and HGL is equal to the kinetic head. For a pipe of uniform cross-section, there will be no change in the velocity of flow across the pipe. Since the kinetic head remian constant, the slope of HGL will be equal than that of EGL.

**11. For a nozzle, the vertical intercept between EGL and HGL**

a) increases

b) decreases

c) remains constant

d) may increase or decrease

Answer: a

Explanation: The vertical intercept between EGL and HGL is equal to the kinetic head. For a nozzle, the cross-sectional area decreases in the direction of flow leading to an increase in the velocity of flow across the pipe. Since the kinetic head increases, the vertical intercept between EGL and HGL will increase.

**12. For a diffuser, the vertical intercept between EGL and HGL**

a) increases

b) decreases

c) remains constant

d) may increase or decrease

Answer: b

Explanation: The vertical intercept between EGL and HGL is equal to the kinetic head. For a diffuser, the cross-sectional area increases in the direction of flow leading to a decrease in the velocity of flow across the pipe. Since the kinetic head decreases, the vertical intercept between EGL and HGL will decrease.

**13. 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

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.

**14. 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

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.

**15. 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

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.

**16. 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

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.

**17. How do we determine the total discharge through parallel pipes?**

a) Add them.

b) Subtract them

c) Multiply them

d) Divide them

Answer: a

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.

**18. 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

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.

**19. 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

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.

**20. When a gas is pushed through a pipe, the gaseous molecules are _________ by the pipe’s walls**

a) Attracted

b) Absorbed

c) Deflected

d) Dissipated

Answer: c

Explanation: This is because there is no attractive force present in the tube for the process of attraction to occur. Also, the surface of pipes is not an absorbing one, hence absorption is also ruled out. A pipe is not capable of dissipation of the molecules. Hence, the right option is deflected.

**21. If the speed of sound is much ________ than that of the gas, the gas density will stay constant.**

a) Smaller

b) Larger

c) Equal to

d) Non-existent

Answer: b

Explanation: This is because only with speed of sound Is larger, it’ll be able to compensate for the speed of gas. Under such situations, the gas density will be able to stay constant. If they are equal, density will get compressed.

**22. Isentropic nozzle flow states about the movement of a gas or fluid through a narrow orifice without an increase or decrease in ___________**

a) Pressure

b) Energy

c) Displacement

d) Entropy

Answer: d

Explanation: Entropy is defined as the measure of degree of randomness. It is a thermodynamics quantity. As this nozzle flow deals with thermodynamics, entropy is the right choice. The other options are not parameters of entropy.

**23. In fluid dynamics, the velocity of the fluid in the stagnation point is**

a) Zero

b) Infinite

c) Non-existent

d) Negative

Answer: a

Explanation: Stagnant point is a point where there is no movement of the fluid. When there is no movement, the velocity will be 0. Hence the answer is 0.

**24. The stagnation state is obtained after a _____________ to zero velocity.**

a) Accelerating

b) Decelerating

c) Equilibrium

d) Exponential increase

Answer: b

Explanation: Initially the flow has a velocity. In the stagnant state, the velocity is 0. For this to happen, there should be a deceleration of the velocity. Hence, deceleration is the answer.

**25. To refrain from separation in subsonic nozzles, the expansion angle must not be more than _____**

a) 10 degrees

b) 20 degrees

c) 30 degrees

d) 40 degrees

Answer: a

Explanation: If the angle is more than 10 degrees, there will be a drift amidst the nozzle. At any angle more than 10 degrees, this separation will occur. But the minimum value is 10 degrees. So, the answer is 10 degrees.

**26. Gas flows through the nozzle from an area of _____ pressure (called the chamber) to one of _____ pressure**

a) High, low

b) Low, high

c) Same, same

d) Constant, Infinite

Answer: a

Explanation: Anything that flows or runs moves from a region of higher value to lower value. We can take the example of any physical parameter like pressure, altitude etc. Hence, here the gas will flow from high to low pressure regions.

**1. The main property that affects a boundary layer is__________**

a) Temperature

b) Pressure

c) Viscosity

d) Surface tension

Answer: c

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.

**2. The layer that is influenced by a planetary boundary is called______**

a) Atmospheric boundary layer

b) Lithosphere

c) Troposphere

d) Hydrosphere

Answer: a

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.

**3. 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

Answer: c

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.

**4. Eddy viscosity is a turbulent transfer of_________**

a) Fluid

b) Heat

c) Momentum

d) Pressure

Answer: c

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.

**5. The laminar boundary layer is a _________**

a) Smooth flow

b) Rough flow

c) Uniform flow

d) Random flow

Answer: a

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.

**6. The turbulent boundary layer is a _________**

a) Non-uniform with swirls

b) Uniform

c) Less stable

d) Smooth

Answer: a

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.

**7. How do we measure the flow rate of liquid?**

a) Coriolis method

b) Dead weight method

c) Conveyor method

d) Ionization method

Answer: a

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.

**8. 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

Answer: c

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.

**9. 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

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.

**10. How can we determine whether the flow is laminar or turbulent?**

a) Reynold’s number

b) Mach number

c) Froude number

d) Knudsen number

Answer: a

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.

**11. The flow separation occurs when the fluid travels away from the __________**

a) Surface

b) Fluid body

c) Adverse pressure gradient

d) Inter-molecular spaces

Answer: c

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.

**12. The swirl caused due to eddies are called as ______**

a) Vortices

b) Vertices

c) Volume

d) Velocity

Answer: a

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.

**13. Eddy viscosity is a turbulent transfer of_________**

a) Fluid

b) Heat

c) Momentum

d) Pressure

Answer: c

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.

**14. Which among the following is a device that converts a laminar flow into a turbulent flow?**

a) Dead Weight Gauge

b) Vacuum Gauge

c) Turbulator

d) Ionization Gauge

Answer: c

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”.

**15. Boundary layer separation does not undergo detachment.**

a) True

b) False

Answer: b

Explanation: Boundary layer separation undergoes detachment from the surface into a broader wake. It occurs mainly when the portion of the boundary layer is closest to the wall. It leads to reverse in the flow direction.

**16. With the boundary layer separation, displacement thickness________**

a) Increases

b) Decreases

c) Remains Same

d) Independent

Answer: a

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.

**17. 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

Answer: d

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.

**18. What is the dimension for drag coefficient?**

a) Newton/s

b) m/s

c) kg/N

d) Dimensionless

Answer: d

Explanation: In fluid dynamics, the drag coefficient has no dimensions. It is a dimensionless quantity. Drag coefficient is used to quantify the resistance of an object in a fluid environment. It is mainly used in air and water.

**19. Skin friction acts on the component of _________**

a) Profile drag

b) Surface blade

c) Vane angles

d) Parallel movement

Answer: a

Explanation: Skin friction acts on the component of profile drag. Pressure drag is also called as form drag. It mainly arises because of the shape of the object. Thus, the correct answer is profile drag.

**20. Bodies with a larger cross section will have________**

a) Lower drag

b) Higher drag

c) Same drag

d) No drag

Answer: b

Explanation: Bodies with a larger cross section will have higher drag. Pressure drag is also called as form drag. It mainly arises because of the shape of the object. Thus, the correct option ‘b’.

**21. Drag coefficient is a function of _________**

a) Mach number

b) Froude’s number

c) Laminar flow

d) Reynolds number

Answer: a

Explanation: Drag coefficient is a function of Mach number. In fluid dynamics, the drag coefficient has no dimensions. It is a dimensionless quantity. Drag coefficient is used to quantify the resistance of an object in a fluid environment.

**22. For a streamlined body to achieve low drag coefficient, the boundary layer must_________**

a) Flow over the body

b) Be attached to the body

c) Move away from the body

d) Move parallel to the body

Answer: b

Explanation: For a streamlined body to achieve low drag coefficient, the boundary layer must be attached to the surface of the body for a long time as possible. This causes the wake to be narrow.

**23. There will be a transition from laminar flow to turbulent flow when______**

a) Reynolds number increases

b) Reynolds number decreases

c) Reynolds number is the same

d) Froude’s number increases

Answer: a

Explanation: There will be a transition from laminar flow to turbulent flow with the increase in the Reynolds number. Reynolds number below 2000 is laminar flow and Reynolds number above 2000 is for turbulent flow.

**24. With the increase in flow velocity, Reynolds number_________**

a) Increases

b) Decreases

c) Same

d) Independent

Answer: a

Explanation: With the increase in flow velocity, Reynolds number increases. Reynolds number below 2000 is laminar flow and Reynolds number above 2000 is for turbulent flow. Thus, the correct option is Increases.

**25. With the decrease in the viscosity, Reynolds number ________**

a) Increases

b) Decreases

c) Same

d) Independent

Answer: a

Explanation: With the decrease in viscosity, Reynolds number increases. Reynolds number below 2000 is laminar flow and Reynolds number above 2000 is for turbulent flow. Thus, the correct option is Increases.

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