1000+ Fluid Mechanics MCQ for RRB ALP [Solved]

1. According to Bazin's formula, the discharge over a rectangular weir is mL2g x H^3/2where m is equal to
A. 0.405 + (0.003/H)
B. 0.003 + (0.405/H)
C. 0.405 + (H/0.003)
D. 0.003 + (H/0.405)
Answer : A

2. 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

3. 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

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

5. The vapour pressure over the concave surface is
A. Less man the vapour pressure over the plane surface
B. Equal to the vapour pressure over the plane surface
C. Greater than the vapour pressure over the plane surface
D. Zero
Answer : A

6. 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

7. A compound pipe is required to be replaced by a new pipe. The two pipes are said to be equivalent, if
A. Length of both the pipes is same
B. Diameter of both the pipes is same
C. Loss of head and discharge of both the pipes is same
D. Loss of head and velocity of flow in both the pipes is same
Answer : C

8. The discharge over a rectangular notch is (where b = Width of notch, and H = Height of liquid, above the sill of the notch)
A. (2/3) C_d × b × ?(2gH)
B. (2/3) C_d × b × ?(2g) × H
C. (2/3) C_d × b × ?(2g) × H^3/2
D. (2/3) C_d × b × ?(2g) × H²
Answer : C

9. 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

10. 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

11. For pipes, turbulent flow occurs when Reynolds number is
A. Less than 2000
B. Between 2000 and 4000
C. More than 4000
D. Less than 4000
Answer : C

12. With an increase in size of tube, the rise or depression of liquid in the tube due to surface tension will
A. Decrease
B. Increase
C. Remain unchanged
D. Depend upon the characteristics of liquid
Answer : A

13. 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

14. The discharge through a small rectangular orifice is given by (where Cd = Coefficient of discharge for the orifice, a = Cross-sectional area of the orifice, h = Height of the liquid above the centre of the orifice)
A. Q = Cd × a × 2gh
B. Q = (2/3). Cd × a × h
C. Q = (Cd × a)/?(2gh)
D. Q = (3Cd × a)/?(2h)
Answer : A

15. An average value of coefficient of velocity is
A. 0.62
B. 0.76
C. 0.84
D. 0.97
Answer : D

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

17. The value of bulk modulus of a fluid is required to determine
A. Reynold's number
B. Froude's number
C. Mach number
D. Euler's number
Answer : C

18. A vertical wall is subjected to a pressure due to one kind of liquid, on one of its sides. The total pressure on the wall per unit length is (where w = Specific weight of liquid, and H = Height of liquid)
A. wH
B. wH/2
C. wH²/2
D. wH²/3
Answer : C

19. 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

20. The resultant upward pressure of the fluid on an immersed body is called
A. Up-thrust
B. Buoyancy
C. Center of pressure
D. All the above are correct
Answer : B

21. The centre of gravity of the volume of the liquid displaced is called
A. Centre of pressure
B. Centre of buoyancy
C. Metacentre
D. None of these
Answer : B

22. Which of the following meters is not associated with viscosity?
A. Red wood
B. Say bolt
C. Engler
D. Orsat
Answer : D

23. The value of the coefficient of compressibility for water at ordinary pressure and temperature in kg/cm is equal to
A. 2100
B. 2700
C. 10,000
D. 21,000
Answer : D

24. The discharge over the trapezoidal notch is equal to the discharge over the rectangular notch __________ the discharge over the triangular notch.
A. Plus
B. Minus
C. Divide
D. None of these
Answer : A

25. In the case of steady flow of a fluid, the acceleration of any fluid particle is
A. Constant
B. Variable
C. Zero
D. Zero under limiting conditions
Answer : C

26. The upper surface of a weir over which water flows is known is
A. Crest
B. Nappy
C. Sill
D. Weir top
Answer : C

27. A body floating in a liquid is said to be in neutral equilibrium, if its metacentre
A. Coincides with its centre of gravity
B. Lies above its centre of gravity
C. Lies below its centre of gravity
D. Lies between the centre of buoyancy and centre of gravity
Answer : A

28. An open tank containing liquid is made to move from rest with a uniform acceleration. The angle 0 which the free surface of liquid makes with the horizontal is such that (where a = Horizontal acceleration of the tank, and g = Acceleration due to gravity)
A. tan? = a/g
B. tan? = 2 a/g
C. tan? = a/2g
D. tan? = a2/2g
Answer : A

29. The discharge through a channel of circular section will be maximum when the depth of water is __________ the diameter of the circular channel.
A. 0.34 times
B. 0.67 times
C. 0.81 times
D. 0.95 times
Answer : D

30. 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

31. Select the correct statement
A. Local atmospheric pressure depends upon elevation of locality only
B. Standard atmospheric pressure is the mean local atmospheric pressure a* sea level
C. Local atmospheric pressure is always below standard atmospheric pressure
D. A barometer reads the difference between local and standard atmospheric pressure
Answer : B

32. Bulk modulus of a fluid __________ as the pressure increases.
A. Remain same
B. Decreases
C. Increases
D. None of these
Answer : C

33. For a floating body to be in stable equilibrium, its metacentre should be
A. Below the center of gravity
B. Below the center of buoyancy
C. Above the center of buoyancy
D. Above the center of gravity
Answer : D

34. When a body is placed over a liquid, it will float 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 : B

35. A flow is called super-sonic if the
A. Velocity of flow is very high
B. Discharge is difficult to measure
C. Mach number is between 1 and 6
D. None of these
Answer : C

36. 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

37. When a cylindrical vessel, containing some liquid, is rotated about its vertical axis, the liquid surface is depressed down at the axis of its rotation and rises up near the walls of the vessel on all sides. This type of flow is known as
A. Steady flow
B. Turbulent flow
C. Vortex flow
D. Uniform flow
Answer : C

38. Choose the wrong statement
A. The center of buoyancy is located at the center of gravity of the displaced liquid
B. For stability of a submerged body, the center of gravity of body must lie directly below the center of buoyancy
C. If C.G. and center of buoyancy coincide, the submerged body must lie at neutral equilibrium for all positions
D. All floating bodies are stable
Answer : D

39. 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

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

41. 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

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

43. 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

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

45. Fluid is a substance which offers no resistance to change of
A. Pressure
B. Flow
C. Shape
D. Volume
Answer : C

46. Euler's dimensionless number relates the following
A. Inertial force and gravity
B. Viscous force and inertial force
C. Viscous force and buoyancy force
D. Pressure force and inertial force
Answer : D

47. 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

48. Surface tension has the units of
A. Newton-sec/m
B. Newton-m/sec
C. Newton/m
D. Newton
Answer : C

49. The mass of 2.5 m3 of a certain liquid is 2 tonnes. Its mass density is
A. 200 kg/m³
B. 400 kg/m³
C. 600 kg/m³
D. 800 kg/m³
Answer : D

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