Fluid Mechanics MCQ Solved Paper for IBPS RRB

1. The hydraulic mean depth for a circular pipe of diameter (d) is
A. d/6
B. d/4
C. d/2
D. d
Answer : B

2. The total energy of each particle at various places in the case of perfect incompressible fluid flowing in continuous stream
A. Keeps on increasing
B. Keeps on decreasing
C. Remain constant
D. May increase/decrease
Answer : C

3. The density of water is 1000 kg/m3 at
A. 0° C
B. 0° K
C. 4° C
D. 20° C
Answer : C

4. When a cylindrical vessel containing liquid is revolved about its vertical axis at a constant angular velocity, the pressure
A. Varies as the square of the radial distance
B. Increases linearly as its radial distance
C. Increases as the square of the radial distance
D. Decreases as the square of the radial distance
Answer : A

5. The length of the divergent cone in a Venturimeter is __________ that of the convergent cone.
A. Equal to
B. Double
C. Three to four times
D. Five to six times
Answer : C

6. The increase in pressure at the outer edge of a drum of radius (r) completely filled up with liquid of density (?) and rotating at (?) rad/s is
A. ? ?² r²
B. 2? ?² r²
C. ? ?² r²/2
D. ? ?² r²/4
Answer : C

7. The conditions for the stable equilibrium of a floating body are
A. The metacentre should lie above the center of gravity
B. The center of buoyancy and the center of gravity must lie on the same vertical line
C. A righting couple should be formed
D. All the above are correct
Answer : D

8. Two pipe systems can be said to be equivalent, when the following quantities are same
A. Friction loss and flow
B. Length and diameter
C. Flow and length
D. Friction factor and diameter
Answer : A

9. According to equation of continuity,
A. w₁a₁ = w₂a₂
B. w₁v₁ = w₂v₂
C. a₁v₁ = a₂v₂
D. a₁/v₁ = a₂/v₂
Answer : C

10. In an internal mouthpiece, the absolute pressure head at vena contracta is __________ the atmospheric pressure head by an amount equal to height of the liquid above the vena contracta.
A. Less than
B. More than
C. Equal to
D. None of these
Answer : A

11. Bernoulli equation deals with the law of conservation of
A. Mass
B. Momentum
C. Energy
D. Work
Answer : C

12. A fluid whose viscosity does not change with the rate of deformation or shear strain is known as
A. Real fluid
B. Ideal fluid
C. Newtonian fluid
D. Non-Newtonian fluid
Answer : C

13. Piezometer is used to measure
A. Pressure in pipe, channels etc.
B. Atmospheric pressure
C. Very low pressures
D. Difference of pressure between two points
Answer : C

14. The variation in the volume of a liquid with the variation of pressure is called its
A. Surface tension
B. Compressibility
C. Capillarity
D. Viscosity
Answer : B

15. The discharge over a rectangular weir, considering the velocity of approach, is (whereH1 = H + Ha = Total height of water above the weir, H = Height of water over the crest of the weir, and Ha = Height of water due to velocity of approach)
A. (2/3) Cd × L.?2g [H1 - Ha]
B. (2/3) Cd × L. ?2g [H1 ^3/2 - Ha ^3/2]
C. (2/3) Cd × L.?2g [H1 ² - Ha ²]
D. (2/3) Cd × L. ?2g [H1 ^5/2 - Ha ^5/2]
Answer : B

16. When the water level on the downstream side of a weir is above the top surface of a weir, the weir is known as
A. Narrow-crested weir
B. Broad-crested weir
C. Ogee weir
D. Submerged weir
Answer : D

17. 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

18. The specific weight of water in S.I. units is taken as
A. 9.81 kN/m³
B. 9.81 × 10³ N/m³
C. 9.81 × 10^-6 N/mm³
D. Any one of these
Answer : D

19. The unit of dynamic viscosity in S.I. units is
A. N-m/s²
B. N-s/m²
C. Poise
D. Stoke
Answer : B

20. Pressure of the order of 10 torr can be measured by
A. Bourdon tube
B. Pirani Gauge
C. Micro-manometer
D. Lonisation gauge
Answer : D

21. The volumetric change of the fluid caused by a resistance is known as
A. Volumetric strain
B. Volumetric index
C. Compressibility
D. Adhesion
Answer : C

22. The pressure in the air space above an oil (sp. gr. 0.8) surface in a tank is 0.1 kg/cm. The pressure at 2.5 m below the oil surface will be
A. 2 metres of water column
B. 3 metres of water column
C. 3.5 metres of water column
D. 4 m of water column
Answer : B

23. Steady flow occurs when
A. The direction and magnitude of the velocity at all points are identical
B. The velocity of successive fluid particles, at any point, is the same at successive 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 patterns are identical in each plane
Answer : B

24. The divergent portion of a Venturimeter is made longer than convergent portion in order to
A. Avoid the tendency of breaking away the stream of liquid
B. To minimise frictional losses
C. Both (A) and (B)
D. None of these
Answer : C

25. The force present in a moving liquid is
A. Inertia force
B. Viscous force
C. Gravity force
D. All of these
Answer : D

26. Barometer is used to measure
A. Velocity of liquid
B. Atmospheric pressure
C. Pressure in pipes and channels
D. Difference of pressure between two points in a pipe
Answer : B

27. In a depressed nappe
A. The pressure below the nappe is atmospheric
B. The pressure below the nappe is negative
C. The pressure above the nappe is atmospheric
D. The pressure above the nappe is negative
Answer : B

28. The total energy line lies over the centre line of the pipe by an amount equal to
A. Pressure head
B. Velocity head
C. Pressure head + velocity head
D. Pressure head - velocity head
Answer : C

29. The unit of surface tension is
A. N/m
B. N/m²
C. N/m³
D. N-m
Answer : A

30. The ratio of the inertia force to the elastic force is called
A. Reynold's number
B. Froude's number
C. Weber's number
D. Mach number
Answer : D

31. When an internal mouthpiece is running free, the discharge through the mouthpiece is: (where a = Area of mouthpiece, and H = Height of liquid above the mouthpiece)
A. 0.5 a. ?2gH
B. 0.707 a. ?2gH
C. 0.855 a. ?2gH
D. a. ?2gH
Answer : A

32. If the depth of water in an open channel is less than the critical depth, the flow is called
A. Critical flow
B. Turbulent flow
C. Tranquil flow
D. Torrential flow
Answer : D

33. The Newton's law of resistance is based on the assumption that the
A. Planes of the body are completely smooth
B. Space around the body is completely filled with the fluid
C. Fluid particles do not exert any influence on one another
D. All of the above
Answer : D

34. According to Darcy's formula, the loss of head due to friction in the pipe is (where f = Darcy's coefficient, l = Length of pipe, v = Velocity of liquid in pipe, and d = Diameter of pipe)
A. flv²/2gd
B. flv²/gd
C. 3flv²/2gd
D. 4flv²/2gd
Answer : D

35. The dynamic viscosity of the liquid __________ with rise in temperature.
A. Remain unaffected
B. Increases
C. Decreases
D. None of these
Answer : C

36. Viscosity of water in comparison to mercury is
A. Higher
B. Lower
C. Same
D. Higher/lower depending on temperature
Answer : A

37. A jet of water discharging from a 40 mm diameter orifice has a diameter of 32 mm at its vena contracta. The coefficient of contraction is
A. 0.46
B. 0.64
C. 0.78
D. 0.87
Answer : B

38. The velocity of the liquid flowing through the divergent portion of a Venturimeter
A. Remains constant
B. Increases
C. Decreases
D. Depends upon mass of liquid
Answer : C

39. When a liquid is flowing through a pipe, the velocity of the liquid is
A. Maximum at the centre and minimum near the walls
B. Minimum at the centre and maximum near the walls
C. Zero at the centre and maximum near the walls
D. Maximum at the centre and zero near the walls
Answer : A

40. The loss of pressure head in case of laminar flow is proportional to
A. Velocity
B. (Velocity)²
C. (Velocity)³
D. (Velocity)⁴
Answer : A

41. The efficiency of power transmission through pipe is (where H = Total supply head, and hf = Head lost due to friction in the pipe)
A. (H - hf )/H
B. H/(H - hf )
C. (H + hf )/H
D. H/(H + hf )
Answer : A

42. Dimensions of surface tension are
A. ML°T?²
B. ML°T
C. ML r²
D. ML²T²
Answer : A

43. One poise is equal to
A. 0.1 N-s/m²
B. 1 N-s/m²
C. 10 N-s/m²
D. 100 N-s/m²
Answer : A

44. Choose the wrong statement
A. Viscosity of a fluid is that property which determines the amount of its resistance to a shearing force
B. Viscosity is due primarily to interaction between fluid molecules
C. Viscosity of liquids decreases with increase in temperature
D. Viscosity of liquids is appreciably affected by change in pressure
Answer : D

45. The hydraulic mean depth or the hydraulic radius is the ratio of
A. Area of flow and wetted perimeter
B. Wetted perimeter and diameter of pipe
C. Velocity of flow and area of flow
D. None of these
Answer : A

46. The Euler's equation for the motion of liquids is based upon the assumption that
A. The fluid is non - viscous, homogeneous and incompressible
B. The velocity of flow is uniform over the section
C. The flow is continuous, steady and along the stream line
D. All of the above
Answer : D

47. Property of a fluid by which molecules of different kinds of fluids are attracted to each other is called
A. Adhesion
B. Cohesion
C. Viscosity
D. Compressibility
Answer : A

48. The power transmitted through a pipe is (where w = Specific weight in N/m³, and Q = Discharge in m³/s)
A. w × Q × H
B. w × Q × hf
C. w × Q (H - hf)
D. w × Q (H + hf)
Answer : C

49. Barometer is used to measure
A. Pressure in pipes, channels etc.
B. Atmospheric pressure
C. Very low pressure
D. Difference of pressure between two points
Answer : B

50. The coefficient of discharge for an external mouthpiece is
A. 0.375
B. 0.5
C. 0.707
D. 0.855
Answer : D