Fluid Mechanics MCQ Solved Paper for RRB NTPC

1. The flow in a pipe is turbulent when Reynold number is
A. Less than 2000
B. Between 2000 and 2800
C. More than 2800
D. None of these
Answer : C

2. 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

3. A vertical wall is subjected to a pressure due to one kind of liquid, on one of its sides. Which of the following statement is correct?
A. The pressure on the wall at the liquid level is minimum
B. The pressure on the bottom of the wall is maximum
C. The pressure on the wall at the liquid level is zero, and on the bottom of the wall is maximum
D. The pressure on the bottom of the wall is zer
Answer : C

4. In a lock-gate, the reaction between two gates is (where P = Resultant pressure on the lock gate, and ? = Inclination of the gate with the normal to the side of the lock)
A. p/sin?
B. 2p/sin?
C. p/2sin?
D. 2p/sin (?/2)
Answer : C

5. 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

6. 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

7. Newton's law of viscosity is a relationship between
A. Shear stress and the rate of angular distortion
B. Shear stress and viscosity
C. Shear stress, velocity and viscosity
D. Pressure, velocity and viscosity
Answer : A

8. The intensity of pressure on an immersed surface __________ with the increase in depth.
A. Does not change
B. Increases
C. Decreases
D. None of these
Answer : B

9. A hemispherical tank of radius (R) has an orifice of cross-sectional area (a) at its bottom and is full of liquid. The time required to empty the tank completely is
A. 14? R^1/2/15C_d × a ?(2g)
B. 14? R^3/2/15C_d × a ?(2g)
C. 14? R^5/2/15C_d × a ?(2g)
D. 14? R^7/2/15C_d × a ?(2g)
Answer : C

10. The tendency of a liquid surface to contract is due to the following property
A. Cohesion
B. Adhesion
C. Viscosity
D. Surface tension
Answer : D

11. Euler's equation in the differential form for the motion of liquids is given by
A. dp/? + g.dz + v.dv = 0
B. dp/? - g.dz + v.dv = 0
C. ?.dp + g.dz + v.dv = 0
D. ?.dp - g.dz + v.dv = 0
Answer : A

12. 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

13. The sheet of water flowing over a notch or a weir is known as
A. Sill or crest
B. Nappe or vein
C. Orifice
D. None of these
Answer : B

14. According to Manning's formula, the discharge through an open channel is (where M = Manning's constant)
A. A × M × m^1/2 × i^2/3
B. A × M × m^2/3 × i^1/2
C. A^1/2 × M^2/3 × m × i
D. A^2/3 × M^1/3 × m × i
Answer : B

15. Pitot tube is used for measurement of
A. Pressure
B. Flow
C. Velocity
D. Discharge
Answer : C

16. The specific weight of sea water is __________ that of pure water.
A. Same as
B. Less than
C. More than
D. None of these
Answer : C

17. The buoyancy depends upon the
A. Weight of the liquid displaced
B. Pressure with which the liquid is displaced
C. Viscosity of the liquid
D. Compressibility of the liquid
Answer : A

18. Mach number is significant in
A. Supersonics, as with projectiles and jet propulsion
B. Full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.
C. Simultaneous motion through two fluids where there is a surface of discontinuity, gravity force, and wave making effects, as with ship's hulls
D. All of the above
Answer : A

19. An internal mouthpiece is said to be running __________ if the length of the mouthpiece is more than three times the diameter of the orifice.
A. Free
B. Partially
C. Full
D. None of these
Answer : C

20. Coefficient of velocity is defined as the ratio of
A. Actual velocity of jet at vena contracta to the theoretical velocity
B. Area of jet at vena contracta to the area of orifice
C. Actual discharge through an orifice to the theoretical discharge
D. None of the above
Answer : A

21. 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

22. In case of flow through parallel pipes,
A. The head loss for all the pipes is same
B. The total discharge is equal to the sum of discharges in the various pipes
C. The total head loss is the sum of head losses in the various pipes
D. Both (A) and (B)
Answer : D

23. The intensity of pressure at any point, in a liquid, is __________ to the depth of liquid from the surface.
A. Equal
B. Directly proportional
C. Inversely proportional
D. None of these
Answer : B

24. A flow whose streamline is represented by a curve, is called
A. One-dimensional flow
B. Two-dimensional flow
C. Three-dimensional flow
D. Four-dimensional flow
Answer : B

25. A weir, generally, used as a spillway of a dam is
A. Narrow crested weir
B. Broad crested weir
C. Ogee weir
D. Submerged weir
Answer : C

26. One litre of water occupies a volume of
A. 100 cm³
B. 250 cm³
C. 500 cm³
D. 1000 cm³
Answer : A

27. A liquid would wet the solid, if adhesion forces as compared to cohesion forces are
A. Less
B. More
C. Equal
D. Less at low temperature and more at high temperature
Answer : B

28. When the Mach number is between __________ the flow is called super-sonic flow.
A. 1 and 2.5
B. 2.5 and 4
C. 4 and 6
D. 1 and 6
Answer : D

29. Ratio of inertia force to elastic force is known as
A. Mach number
B. Froude number
C. Reynolds number
D. Weber's number
Answer : A

30. The flow in which conditions do not change with time at any point, is known as
A. One dimensional flow
B. Uniform flow
C. Steady flow
D. Turbulent flow
Answer : C

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

32. The total pressure on the top of a closed cylindrical vessel of radius (r) completely filled up with liquid of specific weight (w) and rotating at (?) rad/s about its vertical axis, is
A. ? w ?² r²/4g
B. ? w ?² r³/4g
C. ? w ?² r?/4g
D. ? w ?² r²/2g
Answer : C

33. The total pressure on the surface of a vertical sluice gate 2 m x 1 m with its top 2 m surface being 0.5 m below the water level will be
A. 500 kg
B. 1000 kg
C. 1500 kg
D. 2000 kg
Answer : D

34. The absolute pressure is equal to
A. Gauge pressure + atmospheric pressure
B. Gauge pressure - atmospheric pressure
C. Atmospheric pressure - gauge pressure
D. Gauge pressure - vacuum pressure
Answer : A

35. The error in discharge (dQ/Q) to the error in measurement of head (dH/H) over a rectangular notch is given by
A. dQ/Q = (1/2) × (dH/H)
B. dQ/Q = (3/4) × (dH/H)
C. dQ/Q = (dH/H)
D. dQ/Q = (3/2) × (dH/H)
Answer : D

36. The process of diffusion of one liquid into the other through a semi permeable membrane is called
A. Viscosity
B. Osmosis
C. Surface tension
D. Cohesion
Answer : B

37. The property of a fluid which enables it to resist tensile stress is known as
A. Compressibility
B. Surface tension
C. Cohesion
D. Adhesion
Answer : C

38. Which of the following instruments is used to measure flow on the application of Bernoulli's theorem?
A. Venturimeter
B. Orifice plate
C. Nozzle
D. All of the above
Answer : D

39. Water is __________ liquid.
A. A compressible
B. An incompressible
C. Both A and B
D. None of these
Answer : B

40. The depth of the centre of pressure on a vertical rectangular gate 8 m wide and 6 m high, when the water surface coincides with the top of the gate, is
A. 2.4 m
B. 3.0 m
C. 4.0 m
D. 5.0 m
Answer : B

41. The meatcentric height of a ship is 0.6 m and the radius of gyration is 4 m. The time of rolling of a ship is
A. 4.1 s
B. 5.2 s
C. 10.4 s
D. 14.1 s
Answer : C

42. A flow through a long pipe at decreasing rate is called __________ uniform flow.
A. Steady
B. Unsteady
C. Both A and B
D. None of these
Answer : B

43. The pressure less than atmospheric pressure is known as
A. Suction pressure
B. Vacuum pressure
C. Negative gauge pressure
D. All of these
Answer : D

44. A glass tube of smaller diameter is used while performing an experiment for the capillary rise of water because
A. It is easier to see through the glass tube
B. Glass tube is cheaper than a metallic tube
C. It is not possible to conduct this experiment with any other tube
D. All of the above
Answer : A

45. True one-dimensional 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 : A

46. 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

47. The point in the immersed body through which the resultant pressure of the liquid may be taken to act is known as
A. Meta center
B. Center of pressure
C. Center of buoyancy
D. Center of gravity
Answer : B

48. Free surface of a liquid behaves like a sheet and tends to contract to smallest possible area due to the
A. Force of adhesion
B. Force of cohesion
C. Force of friction
D. Force of diffusion
Answer : B

49. Newton's law of viscosity is a relationship between
A. Pressure, velocity and temperature
B. Shear stress and rate of shear strain
C. Shear stress and velocity
D. Rate of shear strain and temperature
Answer : B

50. 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