Hydraulics and Fluid Mechanics MCQ Questions and Answers in Civil Engineering

Question. Flow at constant rate through a tapering pipe is
i) steady flow
ii) uniform flow
iii) unsteady flow
iv) non-uniform flow
The correct answer is
(a) (i) and (ii)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)

Answer : B

Question. For laminar flow in a pipe of circular cross-section, the Darcy’s friction factor f is
(a) directly proportional to Reynolds number and independent of pipe wall roughness
(b) directly proportional to pipe wall roughness and independent of Reynolds number
(c) inversely proportional to Reynolds number and indpendent of pipe wall roughness
(d) inversely proportional to Reynolds number and directly proportional to pipe wall roughness

Answer : C

Question. Resultant pressure of the liquid in the case of an immersed body acts through
(a) center of gravity
(b) center of pressure
(c) metacentre
(d) center of buoyancy

Answer : B

Question. The ratio of average velocity to maximum velocity for steady laminar flow in circular pipes is
(a) 1/2
(b) 2/3
(c) 3/2
(d) 2

Answer : A

Question. For a floating body to be in stable equilibrium, its metacentre should be
(a) below the center of buoyancy
(b) above the center of buoyancy
(c) between e.g. and center of pressure
(d) above the center of gravity.

Answer : D

Question. When a body floating in a liquid, is displaced slightly, it oscillates about
(a) e.g. of body
(b) center of pressure
(c) center of buoyancy
(d) metacentre

Answer : D

Question. In which of the following the friction drag is generally larger than pressure drag?
(a) a circular disc or plate held normal to flow
(b) a sphere
(c) a cylinder
(d) an airfoil

Answer : D

Question. The unit of kinematic viscosity is
(a) gm/cm-sec²
(b) dyne-sec/cm²
(c) gm/cm²-sec
(d) cm²/sec

Answer : D

Question. Drag force is a function of
i) projected area of the body
ii) mass density of the fluid
iii) velocity of the body
The correct answer is
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (i), (ii) and (iii)

Answer : D

Question. The flow which neglects changes in a transverse direction is known as
(a) one dimensional flow
(b) uniform flow
(c) steady flow
(d) turbulent flow

Answer : A

Question. Buoyant force is
(a) resultant force acting on a floating body
(b) equal to the volume of liquid displaced
(c) force necessary to keep a body in equilibrium
(d) the resultant force on a body due to the fluid surrounding it

Answer : D

Question. True one-dimensional flow occurs when
(a) the direction and magnitude of the veiocity at all points are identical
(b) the velocity of successive fluid par-ticles, at any point, is the same at suc-cessive periods of time
(c) the magnitude and direction of the velocity do not change from point to point in the fluid
(d) the fluid particles move in plane or parallel planes and the streamline pat-terns are identical in each plane

Answer : A

Question. The resultant of all normal pressures acts
(a) at e.g. of body
(b) at center of pressure
(c) vertically upwards
(d) at metacentre

Answer : B

Question. Flow of water in a pipe about 3 meters in diameter can be measured by
(a) orifice plate
(b) venturi
(c) rotameter
(d) pitot tube

Answer : D

Question. Operation of McLeod gauge used for low pressure measurement is based on the principle of
(a) gas law
(b) Boyle’s law
(c) Charle’s law
(d) Pascal’s law

Answer : B

Question. Choose the wrong statement.
Alcohol is used in manometer, because
(a) its vapour pressure is low
(b) it provides suitable meniscus for the inclined tube
(c) its density is less
(d) it provides longer length for a given pressure difference

Answer : A

Question. An open vessel of water is accelerated up an inclined plane. The free water surface will
(a) be horizontal
(b) make an angle in direction of inclination of inclined plane
(c) make an angle in opposite direction to inclination of inclined plane
(d) any one of above is possible

Answer : C

Question. The increase in meta centric height
i) increases stability
ii) decreases stability
iii) increases comfort for passengers
iv) decreases comfort for passengers
The correct answer is
(a) (i) and (iii)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)

Answer : B

Question. Which of the following instrument can be used for measuring speed of an aeroplane
(a) Venturimeter
(b) Orifice plate
(c) rotameter
(d) pitot tube

Answer : D

Question. Surface energy per unit area of a surface is numerically equal to
(a) atmospheric pressure
(b) surface tension
(c) force of adhesion
(d) force of cohesion

Answer : B

Question. Free surface of a liquid tends to contract to the smallest possible area due to force of
(a) surface tension
(b) viscosity
(c) friction
(d) cohesion

Answer : A

Question. The units of viscosity are
(a) metre²/sec
(b) kg sec/metre
(c) newton-sec/metre²
(d) newton-sec/metre

Answer : C

Question. The surface tension of mercury at normal temperature compared to that of water is
(a) more
(b) less
(c) same
(d) more or less depending on size of glass tube

Answer : A

Question. A bucket of water is hanging from a spring balance. An iron piece is suspended into water without touching sides of bucket from another support. The spring balance reading will
(a) increase
(b) decrease
(c) remain same
(d) increase/decrease depending on depth of immersion

Answer : C

Question. At the centre line of a pipe flowing under pressure where the velocity gradient is zero, the shear stress will be
(a) minimum
(b) maximum
(c) negative value
(d) could be any value

Answer : D

Question. Select the correct statement
(a) Local atmospheric pressure depends upon elevation of locality only
(b) Standard atmospheric pressure is the mean local atmospheric pressure at sea level
(c) Local atmospheric pressure is always below standard atmospheric pressure
(d) A barometer reads the difference be-tween local and standard atmospheric pressure

Answer : B

Question. Newton’s law of viscosity is a relationship between
(a) shear stress anctthejiate of angular distortion
(b) shear stress and viscosity
(c) shear stress, velocity and viscosity
(d) pressure, velocity and viscosity

Answer : A

Question. Coefficient of contraction for an external cylindrical mouthpiece is
(a) 1.00
(b) 0.855
(c) 0.7H
(d) 0.611

Answer : A

Question. Non uniform flow occurs when
(a) the direction and magnitude of the velocity at all points are identical
(b) the velocity of successive fluid par-ticles, at any point, is the same at suc-cessive periods of time
(c) the fluid particles move in plane or parallel planes and the streamline pat-terns are identical in each plane
(d) velocity, depth, pressure, et(c) change from point to point in the fluid flow.

Answer : D

Question. Pressure of the order of 10''' torr can be measured by
(a) Bourdon tube
(b) Pirani Gauge
(c) micro-manometer
(d) ionisastion gauge

Answer : D

Question. If a sphere of diameter 1 cm falls in castor oil of kinematic viscosity 10 stokes, with a terminal velocity of 1.5 cm/sec, the coefficient of drag on the sphere is
(a) less than 1
(b) between 1 and 100
(c) 160
(d) 200

Answer : C

Question. An ideal fluid is
(a) one which obeys Newton’s law of viscosity
(b) frictionless and incompressible
(c) very viscous
(d) frictionless and compressible

Answer : B

Question. Alcohol is used in manometers because
(a) it has low vapour pressure
(b) it is clearly visible
(c) it has low surface tension
(d) it can provide longer column due to low density

Answer : D

Question. Least possible value of correction factor for
i) kinetic energy is zero
ii) kinetic energy is 1
iii) momentum is zero
iv) momentum is 1
The correct statements are
(a) (i) and (iii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (ii) and (iv)

Answer : D

Question. Mercury is often used in barometer because
(a) it is the best liquid
(b) the height of barometer will be less
(c) its vapour pressure is so low that it may be neglected
(d) both (B) and (C)

Answer : D

Question. Specific weight of sea water is more that of pure water because it contains
(a) dissolved air
(b) dissolved salt
(c) suspended matter
(d) all of the above

Answer : D

Question. A perfect gas
(a) has constant viscosity
(b) is incompressible
(c) is of theoretical interest
(d) none of the above.

Answer : D

Question. The total pressure force on a plane area is equal to the area multiplied by the intensity of pressure at the centriod, if
(a) the area is horizontal
(b) the area is vertical
(c) the area is inclined
(d) all of the above

Answer : D

Question. An open cubical tank of 2 m side is filled with water. If the tank is rotated with an acceleration such that half of the water spills out, then the acceleration is equal to
(a) g/3
(b) g/2
(c) 2g/3
(d) g

Answer : D

Question. Choose the wrong statement
(a) fluids are capable of flowing
(b) fluids conform to the shape of the con-taining vessels
(c) when in equilibrium, fluids cannot sustain tangential forces
(d) when in equilibrium, fluids can sustain shear forces

Answer : D

Question. For a floating body to be in equilibrium
(a) meta center should be above e.g.
(b) center of buoyancy and e.g. must lie on same vertical plane
(c) a righting couple should be formed
(d) all of the above

Answer : D

Question. If 850 kg liquid occupies volume of one cubic meter, men 0.85 represents its
(a) specific weight
(b) specific mass
(c) specific gravity
(d) specific density

Answer : C

Question. The normal stress is same in all directions at a point in a fluid
(a) only when the fluid is frictionless
(b) only when the fluid is incompressible and has zero viscosity
(c) when there is no motion of one fluid layer relative to an adjacent layer
(d) irrespective of the motion of one fluid layer relative to an adjacent layer

Answer : C

Question. Fluid is a substance which offers no resistance to change of
(a) pressure
(b) flow
(c) shape
(d) volume

Answer : C

Question. For measuring flow by a venturimeter, if should be installed in
(a) vertical line
(b) horizontal line
(c) inclined line with upward flow
(d) in any direction and in any location.

Answer : D

Question. The Prartdtl mixing length is
(a) zero at the pipe wall
(b) maximum at the pipe wall
(c) independent of shear stress
(d) none of the above

Answer : A

Question. A liquid compressed in cylinder has a volume of 0.04 m³ at 50 kg/cm² and a volume of 0.039 m³ at 150 kg/cm². The bulk modulus of elasticity of liquid is
(a) 400 kg/cm²
(b) 4000 kg/cm²
(c) 40 x 105 kg/cm²
(d) 40 x 106 kg/cm²

Answer : B

Question. The pressure in Pascals at a depth of 1 m below the free surface of a body of water will be equal to
(a) 1 Pa
(b) 91 Pa
(c) 981 Pa
(d) 9810 Pa

Answer : D

Question. According to Bernoulli’s equation for steady ideal fluid flow
(a) principle of conservation of mass holds
(b) velocity and pressure are inversely proportional
(c) total energy is constant throughout
(d) the energy is constant along a stream-line but may vary across streamlines

Answer : D

Question. To avoid vaporisation in the pipe line, the pipe line over the ridge is laid such that it is not more than
(a) 2.4 m above the hydraulic gradient
(b) 6.4 m above the hydraulic gradient
(c) 10.0 m above the hydraulic gradient
(d) 5.0 above the hydraulic gradient

Answer : B

Question. In a two dimensional incompressible steady flow around an airfoil, the stream lines are 2 cm apart at a great distance from the airfoil, where the velocity is 30 m/se(c) The velocity near the airfoil, where the stream lines are 1.5 cm apart, is
(a) 22.5 m/se(c)
(b) 33 m/se(c)
(c) 40 m/se(c)
(d) 90 m/se(c)

Answer : C

Question. A vertical rectangular plane surface is submerged in water such that its top and bottom surfaces are 1.5 m and 6.0 m res-pectively below the free surface. The position of center of pressure below the free surface will be at a distance of
(a) 3.75 m
(b) 4.0 m
(c) 4.2m
(d) 4.5m

Answer : C

Question. Normal depth in open channel flow is the depth of flow corresponding to
(a) steady flow
(b) unsteady flow
(c) laminar flow
(d) uniform flow

Answer : D

Question. Two dimensional flow occurs when
(a) the direction and magnitude of the velocity at all points are identical
(b) the velocity of successive fluid par-ticles, at any point, is the same at suc-cessive periods of time
(c) the magnitude and direction of the velocity do not change from point to point in the fluid
(d) the fluid particles move in plane or parallel planes and the streamline pat-terns are identical in each plane

Answer : D

Question. The horse power transmitted through a pipe is maximum when the ratio of loss of head due to friction and total head supplied is
(a) 1/3
(b) 1/4
(c) 1/2
(d) 2/3

Answer : A

Question. When a liquid rotates at a constant angular velocity about a vertical axis as a rigid body, the pressure intensity varies
(a) linearly with radial distance
(b) as the square of the radial distance
(c) inversely as the square of the radial distance
(d) inversely as the radial distance

Answer : B

Question. The peoperty by virtue of which a liquid opposes relative motion between its different layers is called
(a) surface tension
(b) co-efficient of viscosity
(c) viscosity
(d) osmosis

Answer : C

Question. According to the principle of buoyancy a body totally or partially immersed in a fluid will be lifted up by a force equal to
(a) the weight of the body
(b) more than the weight of the body
(c) less than the weight of the body
(d) weight of the fluid displaced by the body

Answer : D

Question. The region between the separation streamline and the boundary surface of the solid body is known as
(a) wake
(b) drag
(c) lift
(d) boundary layer

Answer : A

Question. The discharge of a liquid of kinematic viscosity 4 cm2/sec through a 8 cm dia-meter pipe is 3200π cm2/se(c) The type of flow expected is
(a) laminar flow
(b) transition flow
(c) turbulent flow
(d) not predictable from the given data

Answer : A

Question. Surface tension has the units of
(a) newtons/m2
(b) newtons/cm
(c) newtons/m
(d) newtons

Answer : C

Question. The density of water is 1000 kg/m3 at
(a) 0°C
(b) 0°K
(c) 4°C
(d) 20°C

Answer : C

Question. The continuity equation pi V,A,= p2V2A2 is based on the following assumption regarding flow of fluid (where pi and p2 are mass densities.)
(a) steady flow
(b) uniform flow
(c) incompressible flow
(d) frictionless flow

Answer : A

Question. The line of action of the buoyant force acts through the
(a) centroid of the volume of fluid vertically above the body
(b) center of the volume of floating body
(c) center of gravity of any submerged body
(d) centriod of the displaced volume of fluid

Answer : D

Question. The shear stress distribution for a fluid flowing in between the parallel plates, both at rest, is
(a) constant over the cross section
(b) parabolic distribution across the section
(c) zero at the mid plane and varies linearly with distance from mid plane
(d) zero at plates and increases linearly to midpoint

Answer : C

Question. Uniform flow occurs when
(a) the flow is steady
(b) the flow is streamline
(c) size and shape of the cross section in a particular length remain constant
(d) size and cross section change uniformly along length

Answer : C

Question. Which of the following is demensionless
(a) specific weight
(b) specific volume
(c) specific speed
(d) specific gravity

Answer : D

Question. The position of center of pressure on a plane surface immersed vertically in a static mass of fluid is
(a) at the centroid of the submerged area
(b) always above the centroid of the area
(c) always below the centroid of the area
(d) none of the above

Answer : C

Question. Fluid is a substance that
(a) cannot be subjected to shear forces
(b) always expands until it fills any container
(c) has the same shear stress.at a point regardless of its motion
(d) cannot remain at rest under action of any shear force

Answer : D

Question. Steady flow occurs when
(a) the direction and magnitude of the velocity at all points are identical
(b) the velocity of successive fluid par-ticles, at any point, is the same at suc-cessive periods of time
(c) the magnitude and direction of the velocity do not change from point to point in the fluid
(d) the fluid particles move in plane or parallel planes and the streamline pat-terns are identical in each plane

Answer : B

Question. Metacentric height is given as the distance between
(a) the center of gravity of the body andthe meta center
(b) the center of gravity of the body and the center of buoyancy
(c) the center of gravity of the body and the center of pressure
(d) center of buoyancy and metacentre

Answer : A

Question. Separation of flow occurs when
(a) the pressure intensity reaches a minimum
(b) the cross-section of a channel is reduced
(c) the boundary layer comes to rest
(d) all of the above

Answer : C

Question. A large Roynold number is indication of
(a) smooth and streamline flow
(b) laminar flow
(c) turbulent flow
(d) highly turbulent flow.

Answer : D

Question. An object having 10 kg mass weighs 9.81kg on a spring balance. The value of ‘g’ at this place is
(a) 10 m/sec2
(b) 9.81 m/sec2
(c) 10.2 m/sec2
(d) 9.75 m/sec2

Answer : B

Question. The theoretical value of coefficient of contraction of a sharp edged orifice is
(a) 0.611
(b) 0.85
(c) 0.98
(d) 1.00

Answer : A

Question. Ay between two stream lines represents
(a) velocity
(b) discharge
(c) head
(d) pressure

Answer : B

Question. The difference of pressure between the inside and outside of a liquid drop is
(a) p =T × r
(b) p = T/r
(c) p = T/2r
(d) p = 2/Tr

Answer : D

Question. Thee horizontal component of buoyant force is
(a) negligible
(b) same as buoyant force
(c) zero
(d) none of the above

Answer : C