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Dear Readers, Welcome to __ Fluid Mechanics Objective Questions__ have been designed specially to get you acquainted with the nature of questions you may encounter during your Job interview for the subject of

a) pressure

b) kinematic viscosity

c) dynamic viscosity

d) surface tension

Ans: c

a) one which obeys Newton's law of viscosity

b) frictionless and incompressible

c) very viscous

d) frictionless and compressible

Ans: b

a) gm/cm-sec2

b) dyne-sec/cm2

c) gm/cm2-sec

d) cm2/sec

Ans: d

a) 0.25

b) 0.50

c) 1.0

d) none of the above

Ans: c

a) decreases with increase in temperature

b) increases with increase in temperature

c) is independent of temperature

d) is independent of pressure for very high pressure intensities

Ans: b

a) intensity of pressure and rate of angular deformation

b) shear stress and rate of angular de¬formation

c) shear stress, viscosity and tempe¬rature

d) viscosity and rate of angular defor¬mation

Ans: b

a) 4 kN/m2

b) 10 kN/m2

c) 12 kN/m2

d) 14 kN/m2

Ans: d

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

Ans: c

a) PA

b) pA sin 9

c) pA cos 9

d) pA tan 9

where p is pressure intensity at centroid of area and A is area of plane surface.

Ans: a

a) 3.75 m

b) 4.0 m

c) 4.2m

d) 4.5m

Ans: c

a) coincides with the centre of gravity

b) coincides with the centroid of the volume of fluid displaced

c) remains above the centre of gravity

d) remains below the centre of gravity

Ans: b

a) rise until its weight equals the buoyant force

b) tend to move downward and it may finally sink

c) float

d) none of the above

Ans: b

a) centre of gravity and centre of buoy-ancy

b) centre of gravity and metacentre

c) centre of buoyancy and metacentre

d) free surface and centre of buoyancy

Ans: b

a) when its metacentric height is zero

b) when the metacentre is above the centre of gravity

c) when the metacentre is below the centre of gravity

d) only when its centre of gravity is below its centre of buoyancy

Ans: b

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)

Ans: b

a) 5kN

b) lOkN

c) 15 kN

d) 20 kN

Ans: b

a) centre of gravity

b) centre of buoyancy

c) centre of pressure

d) metacentre

Ans: c

a) the pressure throughout the liquid mass is atmospheric

b) there will be vacuum in the liquid

c) the pressure in the liquid mass is greater than hydrostatic pressure

d) none of the above

Ans: a

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

Ans: b

a) g/3

b) g/2

c) 2g/3

d) g

Ans: d

a) zero

b) one-fourth its value when cylinder was full

c) one-half its value when cylinder was full

d) cannot be predicted from the given data

Ans: a

a) product of pressure intensity at its centroid and area

b) force on a vertical projection of the curved surface

c) weight of liquid vertically above the curved surface

d) force on the horizontal projection of the curved surface

Ans: b

i) the ball will move to the front

ii) the bubble will move to the front

iii) the ball will move to the rear

iv) the bubble will move to the rear Find out which of the above statements are correct ?

a) (i) and (ii)

b) (i)and(iv)

c) (ii) and (iii)

d) (iii) and (iv)

Ans: b

a) a function of temperature only

b) a physical property of the fluid.

c) dependent on the flow

d) independent of the flow

Ans: c

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)

Ans: b

a) 22.5 m/sec.

b) 33 m/sec.

c) 40 m/sec.

d) 90 m/sec.

Ans: c

a) 0

b) 1

c) 4/3

d) 2

Ans: b

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)

Ans: d

a) 1

b) 4/3

c) 2

d) 4

Ans: c

a) 4/3

b) 3/2

c) 9/4

d) 27/8

Ans: c

a) steady flow

b) uniform flow

c) incompressible flow

d) frictionless flow

where pi and p2 are mass densities.

Ans: a

a) x2y

b) x2-y2

c) cosx

d) x2 + y2

Ans: b

a) free vortex motion

b) forced vortex motion

c) free vortex at centre and forced vortex outside

d) forced vortex at centre and free vortex outside

Ans: d

a) directly proportional to its radial distance from axis of rotation

b) inversely proportional to its radial distance from the axis of rotation

c) inversely proportional to the square of its radial distance from the axis of rotation

d) directly proportional to the square of its radial distance from the axis of rotation

Ans: a

a) steady flow

b) laminar flow

c) uniform flow

d) turbulent flow

Ans: a

a) mass

b) energy

c) momentum

d) none of the above

Ans: a

a) can be zero

b) is never zero

c) is always zero

d) is independent of coordinates

Ans: a

a) velocity at stagnation point

b) stagnation pressure

c) static pressure

d) dynamic pressure

Ans: b

a) discharge

b) velocity of gas

c) pressure intensity of gas

d) pressure intensity of liquid

Ans: b

a) 0.611

b) 0.85

c) 0.98

d) 1.00

Ans: a

a) current meter

b) venturimeter

c) pitot tube

d) hotwire anemometer

Ans: b

a) The pressure intensity at vena contracta is atmospheric.

b) Contraction is least at vena contracta.

c) Stream lines are parallel throughout the jet at vena contracta.

d) Coefficient of contraction is always less than one.

Ans: c

a) pipe diameter

b) throat diameter

c) angle of diverging section

d) both pipe diameter as well as throat diameter

Ans: a

a) 5%

b) 10%

c) 15%

d) 20%

Ans: a

a) H1/2

b) H3'2

c) H5/2

d) H5'4 where H is head.

Ans: c

a) Coefficient of contraction of a venturimeter is unity.

b) Flow nozzle is cheaper than venturimeter but has higher energy loss.

c) Discharge is independent of orientation of venturimeter whether it is horizontal, vertical or inclined.

d) None of the above statement is correct.

Ans: d

a) is independent of Reynolds number

b) decreases with higher Reynolds number

c) is equal to the coefficient of discharge of venturimeter

d) none of the above

Ans: c

a) equal to atmospheric

b) less than atmospheric

c) more than atmospheric

d) none of the above

Ans: b

a) velocity

b) discharge

c) head

d) pressure

Ans: b

a) 0.611

b) 0.707

c) 0.855

d) 1.00

Ans: b

a) slightly less

b) slightly more

c) nearly half

d) equal

Ans: a

a) sudden enlargement

b) sudden contraction

c) gradual contraction or enlargement

d) friction

Ans: d

a) 1.00

b) 0.855

c) 0.7H

d) 0.611

Ans: a

a) sharp edged orifice

b) venturimeter

c) Borda's mouthpiece running full

d) CipoUetti weir

Ans: b

a) H1/2

b) H3/2

c) H5/2

d) H

where H is head.

Ans: d

a) H/3

b) H/2

c) 2 H/5

d) 2 H/3

where H is the available head.

Ans: d

a) Lower critical Reynolds number is of no practical significance in pipe flow problems.

b) Upper critical Reynolds number is significant in pipe flow problems.

c) Lower critical Reynolds number has the value 2000 in pipe flow

d) Upper critical Reynolds number is the number at which turbulent flow changes to laminar flow.

Ans: a

a) 300

b) 337.5

c) 600

d) 675

Ans: d

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

Ans: c

a) x

b) x

c) x

d) x/7

Ans: a

a) log-log plot of friction factor against Reynolds number

b) log-log plot of relative roughness against Reynolds number

c) semi-log plot of friction factor against Reynolds number

d) semi-log plot of friction factor against relative roughness

Ans: a

a) 0.423 D

b) 0.577 D

c) 0.223 D

d) 0.707 D

where D is the depth of flow.

Ans: b

a) x"7

b) x,/2

c) x4/5

d) x3/5

where x is the distance from leading edge.

Ans: c

a) 0.223 R

b) 0.423 R

c) 0.577 R

d) 0.707 R

where R is radius of pipe.

Ans: a

a) less than 1

b) between 1 and 100

c) 160

d) 200

Ans: c

a) at the extreme rear of body

b) at the extreme front of body

c) midway between rear and front of body

d) any where between rear and front of body depending upon Reynolds number

Ans: a

a) highest intensity of pressure occurs around the circumference at right angles to flow

b) lowest pressure intensity occurs at front stagnation point

c) lowest pressure intensity occurs at rear stagnation point

d) total drag is zero

Ans: d

a) a circular disc of plate held normal to flow

b) a sphere

c) a cylinder

d) a streamlined body

Ans: a

a) a circular disc or plate held normal to flow

b) a sphere

c) a cylinder

d) an airfoil

Ans: d

a) constant

b) dependent only on Reynolds number

c) a function of Reynolds number and relative roughness

d) dependent on relative roughness only

Ans: b

a) 0.1

b) 0.01

c) 0.001

d) 0.0001

Ans: b

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

Ans: c

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

Ans: c

a) 1/2

b) 2/3

c) 3/2

d) 2

Ans: a

a) 1/3 R

b) 1/2 R

c) 2/3 R

d) 3/4R

where R is the radius of pipe.

Ans: a

a) laminar flow

b) transition flow

c) turbulent flow

d) not predictable from the given data

Ans: a

a) zero at the pipe wall

b) maximum at the pipe wall

c) independent of shear stress

d) none of the above

Ans: a

a) is constant over the cross-section

b) varies linearly from zero at walls to maximum at centre

c) varies parabolically with maximum at the centre

d) none of the above

Ans: c

a) less than 1 m/sec

b) 1 m/sec

c) 1.5 m/sec

d) 2 m/sec

Ans: b

a) laminar flow

b) transition flow

c) turbulent flow

d) critical flow

Ans: c

a) always occurs before a separation point

b) always occurs after a separation point

c) is a region of high pressure intensity

d) none of the above

Ans: b

a) 0

b) r/2

c) r

d) 2r

Ans: c

a) always above the centre line of pipe

b) never above the energy grade line

c) always sloping downward in the direction of flow

d) all of the above

Ans: b

a) head loss and discharge are same in two systems

b) length of pipe and discharge are same in two systems

c) friction factor and length are same in two systems

d) length and diameter are same in two systems

Ans: a

a) the head loss is same through each pipe

b) the discharge is same through each pipe

c) a trial solution is not necessary

d) the discharge through each pipe is added to obtain total discharge

Ans: b

a) The absolute roughness of a pipe de-creases with time.

b) A pipe becomes smooth after using for long time.

c) The friction factor decreases with time.

d) The absolute roughness increases with time.

Ans: d

a) 1 m

b) 10m

c) 100m

d) none of the above

Ans: c

a) the length of pipe

b) the viscosity of fluid

c) the bulk modulus for the fluid

d) the original head

Ans: c

a) L/4

b) L/3

c) L/2

d) L

Ans: a

a) from reservoir A to reservoirs B and C

b) from reservoir B to reservoirs C and A

c) from reservoir C to reservoirs A and B

d) unpredictable

Ans: c

a) 32 km

b) 20 km

c) 8 km

d) 4 km

Ans: a

a) less than d

b) between d and 1.5 d

c) between 1.5 d and 2d

d) greater than 2d

Ans: a

a) 1/3

b) 1/4

c) 1/2

d) 2/3

Ans: a

a) 0.40 cm

b) 0.20 cm

c) 0.10 cm

d) 0.05 cm

Assume that boundary layer is entirely laminar.

Ans: b

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)

Ans: d

a) d > m > e

b) d > e > m

c) e > m > d

d) e > d > m

Ans: d

a) 16/Re

b) 32/ Re

c) 64/ Re

d) none of the above where R,, is Reynolds number.

Ans: c

i) steady flow

ii) unsteady flow

iii) uniform flow

iv) non-uniform flow

The correct answer is

a) (i) and (iii)

b) (ii) and (iii)

c) (i) and (:v)

d) (ii) and (iv)

Ans: d

a) minimum roughness coefficient

b) least cost

c) maximum area for a given flow

d) minimum wetted perimeter

Ans:

a) rectangle

b) triangle

c) trapezoidal

d) semi-circle

Ans:

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) (iii) and (iv)

Ans:

a) below critical depth to above critical depth

b) above critical depth to below critical depth

c) below critical depth to above normal depth

d) above normal depth to below normal depth

Ans:

a) the slopes of energy grade line, hydraulic grade line and bottom of the channel are same

b) the slopes of energy grade line and hydraulic grade line are same but slope of the bottom of channel is different

c) the slopes of hydraulic grade line and bottom of channel are same but slope of energy grade line is different

d) the slope of energy grade line, hydraulic grade line and bottom of channel are all different.

Ans:

a) less than 500

b) between 500 and 2000

c) between 2000 and 4000

d) greater than 4000

Ans:

a) zero

b) less than one

c) one

d) greater than one

Ans:

a) the total energy line, water surface and bottom of channel are all horizontal

b) the total energy line and water surface are horizontal but bottom of channel is inclined

c) the total energy line, hydraulic gradient line and bottom of channel are all parallel

d) water surface and bottom of channel are parallel to each other but energy grade line is not parallel to them

Ans:

a) is dimensionless

b) has the dimension of velocity

c) has the dimension of discharge

d) has the dimension Ll/2 T1

Ans:

a) venturi flume

b) current meter

c) pitot tube

d) all the above

Ans:

a) 0.50 m

b) 1.20 m

c) 2.50 m

d) 5.50 m

Ans:

a) 0

b) lm

c) 2m

d) 3m

Ans:

a) critical slope

b) mild slope

c) steep slope

d) adverse slope

Ans:

i) increase in depth of sub critical flow

ii) increase in depth of super critical flow

iii) decrease in depth of sub critical flow

iv) decrease in depth of super critical

flow The correct answer is

a) (i) and (ii)

b) (i)and(iv)

c) (ii) and (iii)

d) (iii) and (iv)

Ans:

a) half

b) one-third

c) two-third

d) equal to the total energy of flow

Ans:

a) greater than critical depth

b) equal to critical depth

c) less than critical depth

d) imaginary

Ans:

a) channel with a mild slope

b) channel with a steep slope

c) a horizontal channel

d) all the above

i) Navier Stake's equation

ii) energy equation

iii) continuity equation

iv) momentum equation

The correct answer is

a) only (i) is correct

b) both (ii) and (iii) are correct

c) both (iii) and (iv) are correct

d) (ii), (iii) and (iv) are correct

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