# 280+ Fluid Mechanics and Machinery Solved MCQs

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1.

## The specific gravity of a liquid has

A. the same unit as that of mass density
B. the same unit as that of weight density
C. the same unit as that of specific volume
D. no unit
Explanation: the specific gravity of a liquid is the ratio of two similar quantities (densities) which makes it unitless.
2.

## The specific volume of a liquid is the reciprocal of

A. weight density
B. mass density
C. specific weight
D. specific volume
Explanation: specific volume(v) is defined as the volume(v ) per unit mass(m).
3.

## Which one of the following is the unit of specific weight?

A. n = m3
B. n = m2
C. n = m
D. n = ms
Explanation: specific weight(γ) is defined as the weight(w) per unit volume(v ), i.e.,
4.

## [p] = [m]/[v] = [m] /[L3] = [ML-3].

A. [m1 l-3 t0].
B. [m1 l0 t0].
C. [m0 l-3 t0].
D. [m0 l0 t0].
Explanation: the specific gravity of a liquid is the ratio of two similar quantities (densities) which makes it dimensionless.
5.

## Which one of the following is the

A. [m1 l-3 t0].
B. [m-1 l3 t0].
C. [m-1 l-3 t0].
D. [m0 l3 t0].
Explanation: specific volume(v) is defined as the volume(v ) per unit mass(m). thus, [v] = [v]/[m] = [l3]/[m] = [m-1l3].
6.

## the relation between their specific volumes v1 and v2?

A. v1 > v2
B. v1 < v2
C. v1 = v2
D. cannot be determined due to insufficient information.
Explanation: specific volume(v) is defined as the volume(v ) per unit mass(m).
7.

## mark of one litre and weighed. The weight of the liquid is found to be 6.5 N. The specific weight of the liquid will be

A. 6:5 kn = m3
B. 6:6 kn = m3
C. 6:7 kn = m3
D. 6:8 kn = m3
Answer» A. 6:5 kn = m3
Explanation: specific weight(γ) is defined as the weight(w) per unit volume(v ), i.e.,
8.

## A beaker is filled with a liquid up to the mark of one litre and weighed. The weight of the liquid is found to be 6.5 N. The specific gravity of the liquid will be

A. 0.65
B. 0.66
C. 0.67
D. 0.68
Explanation: specific gravity(s) of a liquid is defined as the ratio of the density of the liquid(pl) to that of water(pw).
9.

## mark of one litre and weighed. The weight of the liquid is found to be 6.5 N. The specific volume of the liquid will be

A. 1 l =kg
B. 1:5 l =kg
C. 2 l =kg
D. 2:5 l =kg
Explanation: specific volume(v) is defined as the volume(v ) per unit mass(m). thus,
10.

## continuity equation is

A. mass conservation
B. zeroth law of thermodynamics
C. first law of thermodynamics
D. energy conservation
Explanation: continuity equation is derived from the mass conservation principle. it states that for an isolated system, the mass of the system must remain constant.
11.

## equation of mass conservation into the conservative integral form, which of these theorems is used?

A. stokes theorem
B. kelvin-stokes theorem
C. gauss-siedel theorem
D. gauss divergence theorem
Explanation: the expansion of non- conservative integral equation gives two volume integral terms. one of these terms representing the mass flow is converted into surface integral using the gauss divergence theorem.
12.

## ρV→. dS→ is positive when

A. the mass flow is outward
B. the mass flow is inward
C. the mass flow is positive
D. the mass flow is negative
Answer» A. the mass flow is outward
Explanation: ds→ always points outwards to the control volume. so, the product ρv→. ds→ is positive when the mass flow is outwards.
13.

## Hydraulic gradient line takes into consideration

A. potential and kinetic heads only
B. potential and pressure heads only
C. kinetic and pressure heads only
D. potential, kinetic and pressure heads
Explanation: hgl is obtained by plotting piezometric head at various points along the axis of the pipe.
14.

## 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. egl always drops in the direction of c
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.
15.

## 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. hgl may or may not in the direction of flow
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.
16.

## Which of the following is true?

A. hgl will never be above egl
B. hgl will never be under egl
C. hgl will never coincide with egl
D. hgl will may or may not be above egl
Answer» A. hgl will never be above egl
Explanation: egl is obtained by plotting total head and hgl is obtained by plotting piezometric head at various points along the axis of the pipe.
17.

## 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. equal than that of egl for a pipe of uniform cross-section
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
18.

## For a nozzle, the vertical intercept between EGL and HGL

A. increases
B. decreases
C. remains constant
D. may increase or decrease
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
19.

## between EGL and HGL

A. increases
B. decreases
C. remains constant
D. may increase or decrease
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.
20.

## Which of the following is true?

A. the slope of egl will always be greater than that of the axis of the pipe
B. the slope of egl will always be smaller than that of the axis of the pipe
C. the slope of egl will always be equal to that of the axis of the pipe
D. the slope of egl will always be independent of that of the axis of the pipe
Answer» D. the slope of egl will always be independent of that of the axis of the pipe
Explanation: egl is obtained by plotting total head at various points along the axis of the pipe.
21.

## the pressure vary with the length of the pipe?

A. linearly
B. parabolic
C. exponential
D. constant
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.
22.

## 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
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.
23.

## 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
Explanation: high reynolds number flows
24.

## 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. ratio of inertia force to viscous force
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.
25.

## 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
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
26.

## 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
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.
27.

## 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. the flow will remain laminar
Explanation: a flow through a circular pipe is said to be laminar when the reynolds
28.

## What can be the maximum diameter of the pipe for the water flow of velocity 1 m/s (ν = 10-6) to be laminar in nature? Assume Lower critical Reynolds number to be 2100.

A. 2.1 mm
B. 21 mm
C. 21 cm
D. 0.21 mm
Explanation: if the reynolds number of the flow is below its lower critical reynolds number, the flow is clearly laminar. the maximum diameter can be found for re = 2100. the diameter comes out to be 2.1 mm.
29.

## Which of the following flows have the highest critical Reynolds number (lower)?

A. flow in a pipe
B. flow between parallel plates
C. flow in an open channel
D. flow around spherical body
Answer» A. flow in a pipe
Explanation: the approximate lower critical reynolds number for flow in a pipe, flow between parallel plates, flow in an open channel and flow around the spherical body are 2000, 1000, 500 and 1 respectively.
30.

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

A. surface
B. fluid body
D. inter-molecular spaces
Explanation: adverse pressure gradient takes place when the static pressure increases. it increases the direction of the flow. adverse pressure gradient plays an important role in flow separation. thus, option c is correct.
31.

## The swirl caused due to eddies are called as

A. vortices
B. vertices
C. volume
D. velocity
Explanation: vortices are a region in a fluid. it takes place when the flow revolves around an axis line. vortices can be straight or curved. they form shapes like smoke rings and whirlpools.
32.

## Eddy viscosity is a turbulent transfer of

A. fluid
B. heat
C. momentum
D. pressure
Explanation: eddy viscosity is a turbulent transfer of momentum by eddies. it gives rise to an internal fluid friction. it is in analogous to the action of molecular viscosity in laminar fluid flow. eddy viscosity takes place on a large scale.
33.

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

B. vacuum gauge
C. turbulator
D. ionization gauge
Explanation: turbulator is a device that converts a laminar flow into a turbulent flow. the turbulent flow can be desired parts of an aircraft or also in industrial applications.
34.

## Boundary layer separation does not undergo detachment.

A. true
B. false
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.
35.

## With the boundary layer separation, displacement thickness

A. increases
B. decreases
C. remains same
D. independent
Explanation: with the boundary layer separation, displacement thickness increases sharply. this helps to modify the outside potential flow and its pressure field. thus, option ‘a’ is the correct choice.
36.

## automatic control scheme during the fluid flow?

A. rotameters
B. pulley plates
C. rotary piston
D. pilot static tube
Explanation: pilot static tube is a system that uses an automatic control scheme to detect pressure. it has several holes connected to one side of the device. these outside holes are called as a pressure transducer, which
37.

A. resistance= 0
B. drag force= 0
C. temperature = 0
Explanation: d’alembert’s paradox states that for an incompressible and inviscid flow potential flow, the drag force is equal to zero. the fluid is moving at a constant velocity with respect to its relative fluid.
38.

## The steady- state flow must satisfy

A. kirchhoff’s law
B. newtons law
C. rutherford’s experiment
D. kepler’s law
Explanation: the steady state flow must satisfy kirchhoff’s first and second law. the first law states that the total flow into the junction equals the total flow away from the junction. second law is called as the law of conservation of mass. it states that between two junctions, the head loss is independent of the path followed.
39.

## depend on the friction factor?

A. pipe diameter
B. fluid density
C. viscosity
D. weight
Explanation: the friction factor(f) depends on the velocity of flow, fluid density, pipe diameter and the viscosity of the pipe.
40.

## How do we calculate losses for a larger range of Reynolds number?

A. moody chart
B. bar chart
C. scatter chart
D. column histogram
Explanation: moody chart is a graph of frictional factor(f) vs reynolds numbers. it gives various values corresponding to the
41.

## Darcy- Weisbach equation gives relation between

A. pressure and temperature
B. mass, volume and pressure
C. head loss and pressure loss
D. pressure loss only
Explanation: darcy-weisbach equation relates the head loss and pressure loss due to friction along a given pipe with a specified length. it contains a dimensionless friction factor called the darcy friction factor. the equation was named after henry darcy and julius weisbach.
42.

## Which among the following is formula for friction factor of circular pipes?

A. 16/re
B. 64/re
C. re/16
D. re/64
Explanation: circular pipes have a diameter treated in a round manner. for a fluid flow which is laminar head loss is directly proportional to the fluid velocity. thus, friction factor is inversely proportional to its velocity. therefore, the correct option is ‘64/re’.
43.

## Loss of head due to friction is

A. directly proportional to hydraulic radius
B. inversely proportional to velocity
C. inversely proportional to hydraulic radius
D. directly proportional to gravitational constant
Explanation: hydraulic radius is one of the properties of a fluid flow in a channel. it controls the water discharge. it also determines the amount of work the channel
44.

## The formula for hydraulic diameter is

A. 4a/p
B. 4ap
C. 4av
D. 4v
Explanation: hydraulic diameter handles the flow in non-circular channels and tubes. the most suitable term to calculate the hydraulic diameter for a round tube is dh= 4a/p. where ‘a’ is the cross-sectional area and ‘p’ is the wetted perimeter.
45.

## What are the reasons for minor head loses in a pipe?

A. friction
B. heat
C. valves and bends
D. temperature
Explanation: minor losses play an important role in calculating the flow, pressure and energy of the piping system. fluid that moves through the pipe carries momentum and energy due to the forces acting on them.
46.

## What happens to the head loss when the flow rate is doubled?

A. doubles
B. same
C. triples
D. four times
Explanation: if the flow rate is doubled, the head loss increases by a factor of four. since, the head loss is directly proportional to the square of the flow rate. option (d) is the correct option.
47.

## Relative roughness is

A. ϵ/d
B. ϵ*d
C. ϵ/dm
D. ϵgd
Explanation: relative roughness is defined as the quantity used to measure the roughness
48.

## pipes can take up

A. pipes of different diameters
B. pipes of the same diameters only.
C. single pipe only
D. short pipes only
Answer» A. pipes of different diameters
Explanation: when pipes of different diameters are connected at its ends to form a pipe, this pipe so developed is called as pipes in series. they might not have to be of the same diameters. but, having the same diameters are better as it avoids the losses so developed.
49.

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

A. sum of losses in each pipe only
B. sum of local losses only
C. sum of local losses plus the losses in each pipe
D. zero
Answer» C. sum of local losses plus the losses in each pipe
Explanation: when the pipes of different diameters are connected in series from end to end to form a pipe line. the total loss so developed is equal to the sum of local losses
50.

## The total head loss for the system is equal to

A. pipe length
B. pipe diameter
C. width of the reservoir
D. height difference of reservoirs
Answer» D. height difference of reservoirs
Explanation: total head loss for a system is equal to the height difference of the reservoirs. height difference is denoted by the letter ‘h’. total head loss can be equated
51.

## that is developed in the pipe?

A. entry
B. exit
C. connection between two pipes
D. liquid velocity
Explanation: liquid velocity in the pipe is the velocity with which the liquid travels through different cross sections of the pipe. it is a vector field which is used to describe the motion of a continuum. the length of flow velocity vector is equal to the flow speed.
52.

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

A. z1-z2
B. c
C. t2-t1
D. s2-s1
Explanation: total head loss for a system is equal to the height difference of the reservoirs. height difference is denoted by the letter ‘h’. total head loss can be equated
53.

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

A. z1-z2
B. zero
C. t2-t1
D. s2-s1
Explanation: total head loss for a system is equal to the height difference of the reservoirs. height difference is denoted by the letter ‘h’. the height difference between the reservoirs is z1-z2. since they are of the same level, z1=z2. therefore, head loss is zero.
54.

## How do we determine the total discharge through parallel pipes?

B. subtract them
C. multiply them
D. divide them
Explanation: total discharge in parallel pipes are determined by adding the discharges so developed in individual pipes. if q1 is the discharge through pipe 1 and q2 is the discharge through pipe 2. then the total discharge through parallel pipes is equal to
55.

## The pipe diameter is

A. directly proportional to fluid density
B. directly proportional to mass flow rate
C. inversely proportional to mass flow rate
D. directly proportional to fluid velocity
Answer» B. directly proportional to mass flow rate
Explanation: the pipe diameter is directly
56.

## Define Viscosity.

A. resistance to flow of object
B. resistance to flow of air
C. resistance to flow of fluid
D. resistance to flow of heat
Answer» C. resistance to flow of fluid
Explanation: viscosity is developed due to the relative motion between two surfaces of fluids at different velocities. it happens due to the shear stress developed on the surface of the fluid.
57.

## Coefficient of friction of a laminar flow is

A. re/16
B. re/64
C. 16/re
D. 64/re
Explanation: coefficient of friction is defined as the value that shows relationship between force and the normal reaction. it is mainly used to find out an object’s normal force and frictional force. thus, it is equal to 16/re.
58.

## TOPIC 3.1 NEED FOR DIMENSIONAL ANALYSIS - METHODS OF DIMENSIONAL ANALYSIS

A. botanical science
B. zoological science
C. chemistry
D. physics
Explanation: chemistry is the science that deals with every substance, its structure, its composition and changes. physics is the study of the natural world, matter, energy and radiation, while biology is the science that deals with the behaviour of living things are called biological sciences.
59.

## Quantum physics deals with macroscopic phenomena.

A. true
B. false
Explanation: classical physics deals with macroscopic phenomena which may be at the laboratory, terrestrial and astronomical.
60.

## Which of the following uses electromagnetic waves?

C. detecting fractures
D. electric motors
Explanation: electromagnetic waves are used in the radio. while radiotherapy and detecting fractures are done by x-rays and electric motor comes under the electric appliance.
61.

## Which is the universal attractive force?

A. electromagnetic force
B. strong nuclear force
C. weak nuclear force
D. gravitational force
Explanation: gravitational force is the force
62.

## Gravitational force is the weakest force in nature.

A. true
B. false
Explanation: gravitational force is the weakest force in nature because it cannot be felt by us on daily basis. electromagnetic force is the strongest force in nature.
63.

## Which of the following is an example of electromagnetic force?

A. motion of moon around earth
B. evolution of stars
C. evolution of galaxies
D. compression of spring
Explanation: when a spring is compressed, it exerts a force of elasticity due to the net repulsion/ attraction between the
64.

## Why is climbing a lamp post harder than climbing up a tree?

A. because of parallel friction force
B. because of contact force between the bodies
C. because of van der wall’s force
D. because of rope force
Answer» A. because of parallel friction force
Explanation: sometimes, the electromagnetic contact force between two bodies may have a component acting parallel to the surface of contact. this is called friction. when bodies are placed with their smooth surfaces in contact, they provide only a small parallel component of contact of force and hence
65.

## Gravitational force, despite being a weak force, governs the large scale motion.

A. true
B. false
Explanation: mass is only of one type. so the gravitational force is always attractive.
66.

## When a body is falling freely under gravity, the total mechanical energy remains constant because of which of the following?

A. law of conservation of energy
B. unification of force
C. electromagnetic force
D. gravity
Answer» A. law of conservation of energy
Explanation: according to the law of conservation of energy, energy can neither be created nor can it be destroyed but it can be changed from one form to another. when a body falls freely, under gravity, its potential energy gradually changes into kinetic energy. but its total mechanical energy remains constant at any point of its motion.
67.

## What happens when a bullet is fired from a rifle?

A. the rifle becomes weightless
B. we fall back
C. rifle gives backward kick
D. bullet doesn’t leave the rifle
Answer» C. rifle gives backward kick
Explanation: a rifle gives a backward kick on firing a bullet. before firing, both the
68.

## Similitude is a concept applicable to the testing of

A. mathematical models
B. physical models
C. engineering models
D. chemical models
Explanation: similitude is an essential concept that is applicable to the testing of basic engineering models. a model has a similitude with a real-time application. it shares the same geometry. similarity and similitude are interchangeable at times.
69.

## Which among the following is the main application for Similitude?

A. ships
B. cars
C. hydraulics
D. train
Explanation: similitude plays an important role in various applications. one of the major applications are hydraulics and aerospace engineering. its main purpose is to test the fluid flow at different conditions of scaled model.
70.

## A model of with same shape is

A. geometric similarity
B. kinematic similarity
C. dynamic similarity
D. conditional similarity
Explanation: geometric similarity is a similarity that follows a real-time application. it is model that has the same shape for any sort of application. it is measured in scaled quantities.
71.

## Which among the following have similar fluid streamlines?

A. geometric similarity
B. kinematic similarity
C. dynamic similarity
D. conditional similarity
Explanation: in kinematic similarity, fluid flow of model and real-time application takes place. here, the model and the real application must undergo similar time rates in motion changes. thus, it has similar fluid streamlines.
72.

## Which among the following have the same forces acting on them?

A. geometric similarity
B. kinematic similarity
C. dynamic similarity
D. conditional similarity
Explanation: dynamic similarities have the same forces acting on them. that means, the ratios of all the forces acting on the fluid particles are constant. also, the ratio of the
73.

## All the parameters in a similitude are described using

A. continuum mechanics
B. solid mechanics
C. diesel mechanics
D. aircraft mechanics
Explanation: a branch of mechanics that deals with the analysis of mechanical behaviour of materials and kinematics of materials. they are used for modelling purposes. it is modelled in continuous mass.
74.

## Physical similitude has exactly the same geometric shape of the prototype.

A. true
B. false
Explanation: physical similitude is also called the similitude of shape. it is for modelling the same geometric shape as that of its prototype. which means, that the shape will have to be divided by a scale factor.
75.

## Which among the following is a standard scale for a similitude?

A. 1:250
B. 1:50
C. 1:25
D. 1:100
Explanation: to design a similitude with a specific dimension, we must fix a scale. the standard system has fixed the scale as 1:25. this was fixed for an uniformity in dimensions.
76.

## In similitude, Fapplication=Fmodel*3.44

A. true
B. false
Explanation: a model test was conducted to determine this relation. the force and velocity that were measured in the model are to be scaled. this helps to find the force that can be expected for a real-time application.
77.

A. surface tension
B. diffusivity
C. viscosity
D. kinetics
Explanation: diffusivity is defined as the
78.

## Which among the following is the standard symbol for Archimedes number?

A. a
B. ar
C. ar
D. a
Explanation: the standard symbol for archimedes number is ar. archimedes number in fluid mechanics deals with the motion of fluids. this takes place due to the differences in their densities. it was followed by the archimedes principle.
79.

## symbol for Atwood number?

A. a
B. ar
C. ar
D. a
Explanation: the standard symbol for atwood number is a. atwood’s number in fluid mechanics deals with the onset of instabilities in mixtures of fluid. it is due to the density differences in fluid.
80.

## Which among the following is the standard symbol for Blake number?

A. bi
B. ba
C. bl
D. b
Explanation: the standard symbol for blake number is b or bl. blake number in fluid mechanics deals with geology, fluid mechanics and porous media. it is due to the inertial over the viscous forces in fluid flow through porous media.
81.

## Which among the following is the standard symbol for Darcy friction factor?

A. f
B. fd
C. c
D. cd
Explanation: the standard symbol for darcy friction factor is fd. darcy friction factor in fluid mechanics deals with fractions of pressure losses. this is due to the development of friction in the pipe.
82.

## Fanning friction factor is

A. 0.25 times darcy friction factor
B. same as darcy friction factor
C. 2 times darcy friction factor
D. independent
Answer» A. 0.25 times darcy friction factor
Explanation: fanning friction factor is 0.25 times darcy friction factor. fanning friction factor in fluid mechanics deals fraction of pressure losses due to friction in the pipe.
83.

## symbol for Froude number?

A. f
B. fo
C. fr
D. f
Explanation: the standard symbol for froude number is fr. froude number in fluid mechanics deals with wave and surface behaviour of fluid particles. this is with the ratio of body’s inertia to gravitational forces.
84.

## Which among the following is the formula for Knudsen number?

A. λ⁄l
B. λ⁄2l
C. λ⁄3l
D. λ⁄4l
Explanation: the formula for knudsen number is λ⁄l. knudsen number in fluid mechanics deals with gas dynamics. it is defined as the ratio of the molecular mean free path length to the representative scale length.
85.

## utilization of

A. accelerating mass
B. volume
C. work
D. velocity
Explanation: the principle of fluid mechanics works on the utilization of useful work. the working is based on the force exerted by a fluid jet striking the surface and moving over a series of vanes about its axis.
86.

## fluid mechanics deals with heat transfer. It is

A. backward direction
B. forward direction
C. perpendicular direction
D. parallel movement
Explanation: force exerted by a jet on a moving plate happens in three cases. the three cases are classified depending on their
87.

## The force analysis on a curved vane is understood using

A. velocity triangles
B. angle of the plate
C. vane angles
D. plate dimensions
Explanation: the force analysis on a curved vane is understood using clearly using the study of velocity triangles. there are two types of velocity triangles, inlet velocity triangle and outlet velocity triangle.
88.

## Jet propulsion works on the principle of

A. newton’s first law
B. newton’s second law
C. newton’s third law
D. thermodynamic properties
Explanation: jet propulsion works on the principle of newton’s third law. newton’s third law states that for every action, there is an equal and opposite reaction. thus, the correct option is newton’s third law.
89.

## How is absolute velocity at inlet denoted?

A. v
B. v1
C. c
D. v
Explanation: in a jet propulsion, v1 stands for absolute velocity at the inlet. the main
90.

## The relative velocity is obtained by the equation

A. u – v1
B. v1
C. u*v1
D. u/v1
Explanation: the relative velocity of the jet is denoted as vr1. it is the relative velocity at the inlet to the vane. relative velocity of inlet to the vane is obtained by subtracting vectorially the velocity of the vane with its absolute velocity.
91.

## If the friction is neglected, then

A. vr1 > vr2
B. vr1 < vr2
C. vr1 = vr2
D. vr1 is a zero
Explanation: the relative velocity of the jet is denoted as vr1. it is the relative velocity at the inlet to the vane. relative velocity of inlet to the vane is obtained by subtracting vectorially the velocity of the vane with its absolute velocity. it happens in the same way for vr2. thus, if the friction is neglected, then vr1 = vr2.
92.

## If the pressure remains a constant, then

A. vr1 > vr2
B. vr1 < vr2
C. vr1 = vr2
D. vr1 is a zero
Explanation: the relative velocity of the jet is denoted as vr1. it is the relative velocity at
93.

## from the sea can be taken by the pump.

A. true
B. false
Explanation: through inlet orifices, which are facing the direction of motion of the ship, the water from the sea can be taken by the pump. we can also take the sea water from the pump when the inlet orifices are at right angles with respect to the motion of the ship.
94.

## Jet propulsion of ship is less efficient than screw propeller due to

A. pressure
B. temperature
C. frictional losses
D. wear and tear
Explanation: jet propulsion of ship is less efficient than screw propeller due to large amount of frictional losses developed in the pump and the pipeline. thus, it is rarely used in ships.
95.

## A jet strikes a curved plate at its

A. sides
B. surface
C. centre
D. does not strike
Explanation: a jet strikes a curved plate at its centre. force exerted by a jet on a stationery plate happens in three cases. the
96.

## of jet engine?

A. turbojet
B. ramjet
C. scramjet
D. propulsive jet
Explanation: a jet engine is broadly classified into four types of jet. the four types of jet are turbojet, ramjet, scramjet, and pulse jet. there isn’t anything related to the propulsive jet and thus cannot be the answer.
97.

## decelerates the flow, what increases?

A. pressure
B. temperature
C. volume
D. flow rate
Explanation: when the casing in a centrifugal pump decelerates the flow, pressure in the turbine increases. the diffuser helps this happen. the shape of the diffuser passing present in the centrifugal pump is doughnut shaped.
98.

## while passing

A. pressure energy
B. kinetic energy
C. momentum
D. potential energy
Explanation: the velocity imparted by the impeller is converted into pressure energy. it
99.

## The consequence of Newtons second law is

A. conservation of angular momentum
B. conservation of mass
C. conservation of potential energy
D. conservation of kinetic energy
Answer» A. conservation of angular momentum
Explanation: the consequence of newtons second law is the conservation of angular momentum. this, in accordance with newtons second law, provides the basic details to define parameters in the centrifugal pump.
100.

A. true
B. false