1000+ Fluid Mechanics MCQ for SSC Stenographer [Solved]

1. 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 × 10? kg/cm²
D. 40 × 10? kg/cm²
Answer : B

2. A large Reynold number is indication of
A. Smooth and streamline flow
B. Laminar flow
C. Steady flow
D. Highly turbulent flow
Answer : D

3. An orifice is said to be large, if
A. The size of orifice is large
B. The velocity of flow is large
C. The available head of liquid is more than 5 times the height of orifice
D. The available head of liquid is less than 5 times the height of orifice
Answer : D

4. 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

5. The imaginary line drawn in the fluid in such a way that the tangent to any point gives the direction of motion at that point, is known as
A. Path line
B. Stream line
C. Steak line
D. Potential line
Answer : B

6. A flow in which the volume of a fluid and its density does not change during the flow is called _________ flow.
A. Incompressible
B. Compressible
C. Viscous
D. None of these
Answer : A

7. When a body is placed over a liquid, it will sink down if
A. Gravitational force is equal to the up-thrust of the liquid
B. Gravitational force is less than the up-thrust of the liquid
C. Gravitational force is more than the up-thrust of the liquid
D. None of the above
Answer : C

8. A flow is called sub-sonic, if the Mach number is
A. Less than unity
B. Unity
C. Between 1 and 6
D. More than 6
Answer : A

9. The total energy line lies over the hydraulic gradient line by an amount equal to the
A. Pressure head
B. Velocity head
C. Pressure head + velocity head
D. Pressure head - velocity head
Answer : B

10. The total pressure on the top of a closed cylindrical vessel completely filled up with a liquid is
A. Directly proportional to (radius)²
B. Inversely proportional to (radius)²
C. Directly proportional to (radius)⁴
D. Inversely proportional to (radius)⁴
Answer : C

11. The speed of sound in a ideal gas varies directly as its
A. Absolute temperature
B. Temperature
C. Density
D. Modulus of elasticity
Answer : A

12. 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 = 2T/r
Answer : D

13. The velocity corresponding to Reynold number of 2000 is called
A. Sub-sonic velocity
B. Super-sonic velocity
C. Lower critical velocity
D. Higher critical velocity
Answer : C

14. Practical fluids
A. Are viscous
B. Possess surface tension
C. Are compressible
D. Possess all the above properties
Answer : D

15. The coefficient of viscosity may be determined by
A. Capillary tube method
B. Orifice type viscometer
C. Rotating cylinder method
D. All of these
Answer : D

16. According to Bernoulli's equation
A. Z + p/w + v²/2g = constant
B. Z + p/w - v²/2g = constant
C. Z - p/w + v²/2g = constant
D. Z - p/w - v²/2g = constant
Answer : A

17. In an external mouthpiece, the absolute pressure head at vena contracta is __________ the atmospheric pressure head by an amount equal to 0.89 times the height of the liquid, above the vena contracta.
A. Less than
B. More than
C. Equal to
D. None of these
Answer : A

18. The purpose of a surge tank is
A. To control the pressure variations due to rapid changes in the pipe line flow
B. To eliminate water hammer possibilities
C. To regulate flow of water to turbines by providing necessary retarding head of water
D. All of the above
Answer : D

19. The coefficient of discharge for an external mouthpiece depends upon
A. Velocity of liquid
B. Pressure of liquid
C. Area of mouthpiece
D. Length of mouthpiece
Answer : D

20. In a short cylindrical external mouthpiece, the vena contracta occurs at a distance __________ the diameter of the orifice from the outlet of orifice.
A. Equal to
B. One-fourth
C. One-third
D. One-half
Answer : B

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

22. The length of a liquid stream while flowing over a weir __________ at the ends of the sill.
A. Expands
B. Does not change
C. Contracts
D. None of these
Answer : C

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

24. The flow in which the particles of a fluid attain such velocities that varies from point to point in magnitude and direction as well as from instant to instant, is known as
A. One dimensional flow
B. Uniform flow
C. Steady flow
D. Turbulent flow
Answer : D

25. The flow in a pipe is neither laminar nor turbulent when Reynold number is
A. Less than 2000
B. Between 2000 and 2800
C. More than 2800
D. None of these
Answer : B

26. Center of pressure compared to e.g. is
A. Above it
B. Below it
C. At same point
D. Above or below depending on area of body
Answer : B

27. A differential manometer is used to measure
A. Atmospheric pressure
B. Pressure in pipes and channels
C. Pressure in Venturimeter
D. Difference of pressures between two points in a pipe
Answer : D

28. The atmospheric pressure at sea level is
A. 103 kN/m²
B. 10.3 m of water
C. 760 mm of mercury
D. All of these
Answer : D

29. The velocity at which the laminar flow stops, is known as
A. Velocity of approach
B. Lower critical velocity
C. Higher critical velocity
D. None of these
Answer : B

30. In order to measure the flow with a Venturimeter, it is installed in
A. Horizontal line
B. Inclined line with flow upwards
C. Inclined line with flow downwards
D. Any direction and in any location
Answer : D

31. 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

32. 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

33. Kinematic viscosity is equal to
A. Dynamic viscosity/density
B. Dynamic viscosity × density
C. Density/dynamic viscosity
D. 1/dynamic viscosity × density
Answer : A

34. The centre of gravity of the volume of the liquid displaced by an immersed body is called
A. Centre of gravity
B. Centre of pressure
C. Metacentre
D. Centre of buoyancy
Answer : D

35. A perfect gas
A. Has constant viscosity
B. Has zero viscosity
C. Is in compressible
D. None of the above
Answer : D

36. 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

37. When the Mach number is less than unity, the flow is called
A. Sub-sonic flow
B. Sonic flow
C. Super-sonic flow
D. Hyper-sonic flow
Answer : A

38. A compound pipe of diameter d1, d2 and d3 having lengths l1, l2 and l3 is to be replaced by an equivalent pipe of uniform diameter d and of the same length (l) as that of the compound pipe. The size of the equivalent pipe is given by
A. l/d² = (l?/d?²) + (l?/d?²) + (l?/d?²)
B. l/d³ = (l?/d?³) + (l?/d?³) + (l?/d?³)
C. l/d? = (l?/d??) + (l?/d??) + (l?/d??)
D. l/d? = (l?/d??) + (l?/d??) + (l?/d??)
Answer : D

39. A square surface 3 m × 3 m lies in a vertical line in water pipe its upper edge at water surface. The hydrostatic force on square surface is
A. 9,000 kg
B. 13,500 kg
C. 18,000 kg
D. 27,000 kg
Answer : B

40. The total pressure on a horizontally immersed surface is (where w = Specific weight of the liquid, A = Area of the immersed surface, and x = Depth of the centre of gravity of the immersed surface from the liquid surface)
A. wA
B. wx
C. wAx
D. wA/x
Answer : C

41. The top of the weir over which the water flows is known as
A. Sill or crest
B. Nappe or vein
C. Orifice
D. None of these
Answer : A

42. An error of 1% in measuring head over the apex of the notch (H) will produce an error of _________ in discharge over a triangular notch.
A. 1 %
B. 1.5 %
C. 2 %
D. 2.5 %
Answer : D

43. 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

44. The Metacentric heights of two floating bodies A and B are 1 m and 1.5 m respectively. Select the correct statement.
A. The bodies A and B have equal stability
B. The body A is more stable than body B
C. The body B is more stable than body A
D. The bodies A and B are unstable
Answer : C

45. The flow in which the velocity vector is identical in magnitude and direction at every point, for any given instant, is known as
A. One dimensional flow
B. Uniform flow
C. Steady flow
D. Turbulent flow
Answer : B

46. In order to increase sensitivity of U-tube manometer, one leg is usually inclined by angle ?. Sensitivity of inclined tube to sensitivity of Utube is equal to
A. Sin?
B. 1/Sin?
C. Cos?
D. 1/Cos?
Answer : B

47. The force exerted by a moving fluid on an immersed body is directly proportional to the rate of change of momentum due to the presence of the body. This statement is called
A. Newton's law of motion
B. Newton's law of cooling
C. Newton's law of viscosity
D. Newton's law of resistance
Answer : D

48. A flow in which the viscosity of fluid is dominating over the inertia force is called
A. Steady flow
B. Unsteady flow
C. Laminar flow
D. Turbulent flow
Answer : C

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

50. In a free 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 : A