# 730+ Fluid Mechanics and Hydraulic Machines Solved MCQs

Chapters

129
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Chapter: Fluids and Their Properties
1.

## The branch of Engineering-science, which deals with water at rest or in motion is called

A. hydraulics
B. Fluid mechanics
C. Applied mechanics
D. Kinematics.
2.

## A solid can resist which of the following stresses?

A. Tensile
B. Compressive
C. Shear
D. All of the above.
Answer» D. All of the above.
3.

A. Solid
B. Liquid
C. Gas
D. Vapour.
4.

## The ratio of the specific weight of the liquid to the specific weight of a standard fluid is known as

A. Specific volume
B. Weight density
C. Specific gravity
D. Viscosity.
5.

## The property of a fluid which determines its resistance to shearing stress is called

A. Viscosity
B. Surface tension
C. Compressibility
D. None of the above.
6.

A. Newtonian
B. Non-Newtonian
C. Dilatant
D. ideal
7.

## The printer’s ink is an example of

A. Newtonian fluid
B. Non-Newtonian
C. Thixotropic substance
D. Elastic solid.
8.

## The viscosity of liquids ..... with increase in temperature.

A. Decreases
B. Increases
C. First decreases and then increases
D. First increases and then decreases.
9.

## Surface tension is caused by the force of ..... at the free surface.

A. Cohesion
C. Both (a) and (b)
D. None of the above.
10.

## Which of the following is an example of phenomenon of surface tension?

A. Rain drops
B. Rise of sap in a tree
C. Break up of liquid jets
D. All of the above.
Answer» D. All of the above.
11.

A. N/m
B. N/m2
C. N2/m
D. N/m3
12.

A. p = 4𝜎/d
B. p = 3𝜎/d
C. p = 8𝜎/d
D. p = 16𝜎/d
13.

## . ...... is a phenomenon by which a liquid rises into a thin glass tube above or below its general level.

A. Surface tension
B. Capillarity
C. Cohesion
14.

A. h = 2σ/wd
B. h = 3σ/wd
C. h = 4σ/wd
D. h = 6σ/wd
15.

## Elasticity of fluids is measured in terms of

A. Young’s modulus of elasticity
B. Shear modulus of elasticity
C. Bulk modulus of elasticity
D. None of the above.
Answer» C. Bulk modulus of elasticity
16.

## Compressibility is the reciprocal of

A. Bulk modulus of elasticity
B. Shear modulus of elasticity
C. Young’s modulus of elasticity
D. Any of the above.
Answer» A. Bulk modulus of elasticity
17.

## Bulk modulus of elasticity is the ratio of

A. Tensile stress to tensile strain
B. Compressive stress to compressive strain
C. Compressive stress to volumetric strain
D. None of the above.
Answer» C. Compressive stress to volumetric strain
18.

## The value of bulk modulus of elasticity .......... with increase of pressure.

A. Increases
B. Decreases
C. Either of the above
D. None of the above.
19.

A. Parallel
B. Normal
C. 45°
D. 60°.
20.

## The pressure ....... as the depth of the liquid increases.

A. Increases
B. Decreases
C. Remain unchanged
D. None of the above.
21.

## The intensity of pressure in a liquid due to its depth will vary .... with depth.

A. Directly
B. Indirectly
C. Either of the above
D. None of the above.
22.

## The height of the free surface above any point is known as

B. Intensity of pressure
C. Either of the above
D. None of the above.
23.

## “The intensity of pressure at any point in a liquid at rest is the same in all directions.” The above statement is known as

A. Kirchhoff’s law
B. Pascal’s law
C. Either of the above
D. None of the above.
24.

## Any pressure measured above the absolute zero of pressure is termed as

A. Atmospheric pressure
B. Gauge pressure
C. Either of the above
D. None of the above
Answer» C. Either of the above
25.

## The fundamental S.I. unit of pressure is N/m2; this is also known as ......

A. Pascal
B. Stoke
C. Poise
D. None of the above
Chapter: Static Forces on Surface and Buoyancy
26.

A. p = wh
B. h = pw
C. p = wh2
D. p = wh3.
27.

## The point of application of the total pressure on the surface is

A. Centroid of the surface
B. Centre of pressure
C. Either of the above
D. None of the above.
28.

## If A is the area of the immersed surface, w is the specific weight of the liquid and ͞x is the depth of horizontal surface from the liquid surface, then the total pressure P on the surface is given by

A. p = wA2 ͞x
B. p = w2A ͞x
C. p = wA ͞x
D. p = wA ͞x2
Answer» C. p = wA ͞x
29.

## The side of the dam to which the water from the river or the stream approaches is known as

A. Downstream
B. Upstream
C. Either of the above
D. None of the above.
30.

## Lock gates are provided to

A. Change the water level in a canal or river for irrigation
B. Store water for irrigation purpose
C. Either of the above
D. None of the above.
Answer» A. Change the water level in a canal or river for irrigation
31.

## The term........ means the study of pressure exerted by a fluid at rest.

A. Hydrostatics
B. Fluid mechanics
C. Continuum
D. Kinetics
32.

## The tendency for an immersed body to be lifted up in the fluid, due to an upward force opposite to the action of gravity is known as

A. Buoyancy
B. Centre of buoyancy
C. Buoyant force
D. None of the above.
33.

## The magnitude of the buoyant force can be determined by

A. Newton’s second law of motion
B. Archimedes’ principle
C. Principle of moments
D. None of the above.
34.

## When a body is immersed in a fluid, partially or completely, the force of buoyancy is equal to

A. The weight of the body
B. The weight of the fluid displaced by the body
C. The weight of the volume of the fluid equal to the volume of body
D. None of the above.
Answer» B. The weight of the fluid displaced by the body
35.

## The point of application of the force of buoyancy on the body is known as

A. Centre of gravity
B. Centre of buoyancy
C. Metacenter
D. None of the above.
36.

A. Archimedes
B. Newton
C. Pascal
D. Kirchhoff.
37.

## A floating body is in stable equilibrium when

A. The metacentre is below its centre of gravity
B. The metacentre is above its centre of gravity
C. The metacentric height is zero.
D. Its centre of gravity is below the centre of buoyancy.
Answer» B. The metacentre is above its centre of gravity
38.

## An ice-cube is floating in glass of water. As the cube melts the water level

A. Remain constant
B. Falls
C. Rises
D. None of the above.
39.

## Metacentric height can be determined by

A. Only analytical method
B. Only experimental method
C. Both (a) and (b)
D. None of the above.
Answer» C. Both (a) and (b)
40.

## If a body does not return to its original position from the slightly displaced angular position and heels farther away, when given a small angular displacement; such an equilibrium is called

A. Stable equilibrium
B. Unstable equilibrium
C. Neutral equilibrium
D. Any of the above
Chapter: Motion of Fluid Particles and Streams
41.

## The motion of fluid particles may be described by which of the following methods?

A. Langrangian method
B. Eulerain method
C. Both (a) and (b)
D. None of the above.
Answer» C. Both (a) and (b)
42.

## In which of the following methods, the observer concentrates on a point in the fluid system?

A. Langrangian method
B. Eulerian method
C. Any of the above
D. None of the above.
Answer» D. None of the above.
43.

## Normal acceleration in fluid-flow situation exists only when

B. The flow is two-dimensional
C. The streamlines are straight and parallel
D. The streamlines are curved.
Answer» B. The flow is two-dimensional
44.

## In a steady flow the velocity

A. Does not change from place to place
B. At a given point does not change with time
C. May change its direction but the magnitude remains unchanged
D. None of the above.
Answer» B. At a given point does not change with time
45.

## The flow in a pipe whose valve is being opened or closed gradually is an example of

C. Rotational flow
D. Compressible flow.
46.

## The type of flow in which the velocity at any given time does not change with respect to space is called

B. Compressible flow
C. Uniform flow
D. Rotational flow.
47.

## Flow in a pipe where average flow parameters are considered for analysis is an example of

A. Incompressible flow
B. One-dimensional flow
C. Two-dimensional flow
D. Three-dimensional flow.
48.

49.

## Flow between parallel plates of infinite extent is an example of

A. One-dimensional flow
B. Two-dimensional flow
C. Three-dimensional flow
D. Compressible flow.
50.

## If the flow is irrational as well as steady it is known as

A. Non-uniform flow
B. One-dimensional flow
C. Potential flow
D. None of the above.
51.

## High velocity flow in a conduit of large size is known as

A. Laminar flow
B. Turbulent flow
C. Either of the above
D. None of the above.
52.

## If the Reynolds number is less than 2000, the flow in a pipe is

A. Laminar flow
B. Turbulent flow
C. Transition flow
D. None of the above.
53.

## The path followed by fluid particle in motion is called a

A. Streamline
B. Path line
C. Streak line
D. None of the above.
54.

## A....is an imaginary line within the flow so that the tangent at any point on it indicates the velocity at that point.

A. Streak line
B. Stream line
C. Path line
D. None of the above.
55.

## A stream line is one

A. In which stream function does not change
B. In which the flow cannot cross the bounding surface
C. Which has a constant area throughout its length so that the velocity remains constant.
D. None of the above.
Answer» B. In which the flow cannot cross the bounding surface
56.

## ...... is a curve which gives an instantaneous picture of the location of the fluid particles which have passed through a given point.

A. Path line
B. Stream line
C. Streak line
D. None of the above.
57.

## In fluid mechanics, the continuity equation is a mathematical statement embodying the principle of

A. Conservation of momentum
B. Conservation of mass
C. Conservation of energy
D. None of the above.
58.

## An irrational flow is one in which

A. The stream lines of flow are curved and closely spaced
B. The fluid does not rotate as it moves along
C. The net rotation of fluid particles about their mass centres remains zero
D. None of the above.
Answer» C. The net rotation of fluid particles about their mass centres remains zero
59.

## In a fluid-flow the stream lines are lines

A. Along which the vorticity is zero
B. Along which the stream function ψ = constant
C. Which are parallel to the equipotential lines
D. Which exist in irrotional flow only.
Answer» B. Along which the stream function ψ = constant
60.

## ....... is defined mathematically as the line integral of the tangential velocity about a closed path (contour).

A. Circulation
B. Vorticity
C. Either of the above
D. None of the above.
61.

## The concept of stream function which is based on the principle of continuity is applicable to

A. Irrotational flow only
B. Two-dimensional flow only
C. Three-dimensional flow
D. Uniform flow only.
62.

## The motion is described as ......when the components of rotation or vorticity are zero throughout certain point of the fluid.

A. Rotational
B. Irrotational
C. Either of the above
D. None of the above.
63.

## ........ is defined as a scalar function of space and time such that its negative derivative with respect to any direction gives the fluid velocity in that direction.

A. Velocity potential function
B. Stream function
C. Circulation
D. Vorticity.
64.

65.

## A flow net is a graphical representation of strea lines and equipotential lines such that these lines

A. Intersect each other orthogonally forming curvilinear squares
B. Intersect each other at various different angles forming irregular-shaped nets
C. Indicate the direction and magnitude of vector
D. None of the above.
Answer» A. Intersect each other orthogonally forming curvilinear squares
Chapter: The Energy Equation and its Application
66.

A. V/g
B. V2/2g
C. V3/2g
D. V2/2g2
67.

## Euler’s equation (in differential form) is written as:

A. dp/ρ + v2.dv + g.dz = 0
B. dp/ρ + v.dv + g.dz = 0
C. dp/ρ + v.dv + g2.dz = 0
D. dp/ρ2 + v.dv + g.dz = 0
Answer» B. dp/ρ + v.dv + g.dz = 0
68.

## In which of the following measuring devices Bernoulli’s equation is used:

A. Venturimeter
B. Orificemeter
C. Pitot tube
D. All the above.
69.

## The co-efficient of discharge of an orificemeter is ......that of a venturimeter.

A. Equal to
B. Much smaller than
C. Much more than
D. Any of these.
70.

## The piezometric head is the summation of :

D. None of the above.
71.

## The total-energy-line in pipe flow is a graphical representation of the Bernoulli’s equation and represents the sum of velocity head, pressure head and the elevation head above:

A. The top of the pipeline
B. The arbitrary horizontal datum
C. The centre line of pipe
D. The bottom of the pipe.
Answer» B. The arbitrary horizontal datum
72.

A. Nm/s
B. Ns/m
C. Nm/m
D. Nm/N.
73.

## The Bernoulli’s equation written in the conventional form p/ρg + V2/2g + z = constant total energy per unit of certain quantity. Identify this quantity from the choices given below:

A. Energy per unit mass
B. Energy per unit weight
C. Energy per unit volume
D. Energy per unit specific weight.
Answer» B. Energy per unit weight
74.

A. Pressure
B. Flow rate
C. Total energy
75.

A. 0.95 to 0.99
B. 0.8 to 0.85
C. 0.7 to 0.8
D. 0.6 to 0.7
76.

## A Pitot-tube is used for measuring:

A. Velocity of flow
B. Pressure of flow
C. Flow rate
D. Total energy.
77.

## When a Pitot-tube is put to use it must be ensured that its alignment is such that:

A. The horizontal leg should be inclined at 45° in plan
B. Its horizontal leg is at right angles to the flow direction
C. Its opening faces upstream and the horizontal leg is perfectly aligned with the direction of flow
D. None of the above.
Answer» C. Its opening faces upstream and the horizontal leg is perfectly aligned with the direction of flow
78.

## The hydraulic gradient-line indicates the variation of which of the following:

A. Velocity head in flow direction
B. Piezometric head in the direction of flow
C. Total energy of flow in the direction of flow
D. None of the above.
79.

## The momentum correction factor β is used to account for:

A. Change in direction of flow
B. Change in total energy
C. Non-uniform distribution of velocities at inlet and outlet sections
D. Change in mass rate of flow.
Answer» C. Non-uniform distribution of velocities at inlet and outlet sections
80.

## The change in moment of momentum of fluid due to flow along a curved path results in:

A. A change in pressure
B. Torque
C. A change in the total energy
D. None of the above.
81.

## Which of the following is an example of free vortex flow?

A. A whirlpool in a river
B. Flow of liquid through a hole provided at the bottom of a container
C. Flow of liquid around a circular bend in a pipe.
D. All of the above.
Answer» D. All of the above.
82.

## In case of forced vortex, the rise of liquid level at the ends is .... the fall of liquid level at the axis of rotation.

A. Less than
B. More than
C. Equal to
D. None of the above
83.

## In case of a closed cylindrical vessel sealed at the top and the bottom the volume of air before rotation is ...... the volume of air after:

A. More than
B. Less than
C. Equal to
D. None of the above
Chapter: Dimensional Analysis and Similarities
84.

## Dimensional analysis is used to

A. Test the dimensional homogeneity of any equation of fluid motion
B. Derive rational formulae for a flow phenomenon
C. Derive equations expressed in terms of non– dimensional parameters
D. All of the above.
Answer» D. All of the above.
85.

## Which of the following is an advantage of dimensional analysis?

A. It expresses the functional relationship between the variables in dimensionless terms
B. In hydraulic model studies it reduces the number of variables involved in a physical phenomenon, generally by three
C. By the use of dimensional analysis design curves can be developed from experimental data or direct solution of the problem
D. All of the above.
Answer» D. All of the above.
86.

## dimensionally homogeneous equation is applicable to

A. C.G.S. system only
B. F.P.S. system only
C. M.K.S. and SI systems
D. All systems of units.
Answer» D. All systems of units.
87.

## In which of the following methods of dimensional analysis, a functional relationship of some variables is expressed in the form of an exponential equation, which must be dimensionally homogeneous?

A. Buckingham’s π-method
B. Rayleigh’s method
C. Bridgman’s method
D. Matrix–tensor method.
88.

## In dimensional analysis the Buckingham’s π–theorem is widely used and expresses the resulting equation in terms of

A. The repeating variables
B. Geometric, kinematic and dynamic variables
C. (n – m) dimensionless parameters
D. n dimensionless parameters.
Answer» C. (n – m) dimensionless parameters
89.

## To apply Buckingham’s π–theorem, m repeating variables are selected from amongst the n variables influencing the phenomenon. The repeating variables are selected such that they

A. Belong to kinematic and dynamic category of variables
B. Must always contain the dependent variables
C. In combination contain each of the m fundamental dimensions involved in the problem.
D. None of the above.
Answer» C. In combination contain each of the m fundamental dimensions involved in the problem.
90.

## In order that results obtained in model studies correctly represent the behaviour of the prototype, which of the following similarities must be ensured between the model and the prototype?

A. Geometric similarity
B. Kinematic similarity
C. Dynamic similarity
D. All of the above.
Answer» D. All of the above.
91.

## Dynamic similarity between the model and prototype is the

A. Similarity of motion
B. Similarity of lengths
C. Similarity of forces
D. None of the above.
92.

## ...... is equal to the product of shear stress due to viscosity and surface area of flow.

A. Viscous force
B. Inertia force
C. Pressure force
D. Gravity force.
93.

## Kinematic similarity between model and prototype is the

A. Similarity of discharge
B. Similarity of shape
C. Similarity of streamline pattern
D. None of the above.
Answer» C. Similarity of streamline pattern
94.

## ......... is the ratio of the inertia force to the viscous force.

A. Froude’s number
B. Weber’s number
C. Reynolds number
D. Mach’s number.
95.

## ........ is the square root of the ratio of the inertia force to the pressure force.

A. Reynolds number
B. Mach’s number
C. Euler’s number
D. Froude’s number.
96.

## Euler number is important in which of the following flow situations?

A. Discharge through orifices, mouthpieces and sluices
B. Pressure rise due to sudden closure of valves
C. Flow through pipes
D. All of the above
Answer» D. All of the above
97.

## Mach’s number is defined as the square root of the ratio of the

A. Inertia force to the pressure force
B. Inertia force to the surface tension force
C. Inertia force to the elastic force
D. None of the above.
Answer» C. Inertia force to the elastic force
98.

## ...... is important in compressible fluid flow problems at high velocities, such as high velocity flow in pipes or motion of high-speed projectiles and missiles.

A. Euler’s number
B. Mach’s number
C. Reynolds number
D. Froude’s number.
99.

## Distorted models are required to be prepared for which of the following?

A. Rivers
B. Dams across very wide rivers
C. Harbours
D. All of the above.
Answer» D. All of the above.
100.

## The scale effect in models can be

A. Positive only
B. Negative only
C. Both positive and negative
D. None of the above.
Answer» C. Both positive and negative