GRE - Fluid Mechanics 1000+ MCQ [Solved] PDF Download

1. The most economical section of a trapezoidal channel is one which has hydraulic mean depth equal to
A. 1/2 × depth
B. 1/2 × breadth
C. 1/2 × sloping side
D. 1/4 × (depth + breadth)
Answer : A

2. 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

3. The coefficient of discharge in case of internal mouthpiece is __________ that of external mouthpiece.
A. Less than
B. More than
C. Equal to
D. None of these
Answer : A

4. Density of water is maximum at
A. 0° C
B. 0° K
C. 4° C
D. 100° C
Answer : C

5. The value of coefficient of velocity for a sharp edged orifice __________ with the head of water.
A. Decreases
B. Increases
C. Remain same
D. None of these
Answer : B

6. Metacentric height is the distance between the metacentre and
A. Water surface
B. Center of pressure
C. Center of gravity
D. Center of buoyancy
Answer : C

7. 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

8. The force per unit length is the unit of
A. Surface tension
B. Compressibility
C. Capillarity
D. Viscosity
Answer : A

9. 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

10. Ratio of inertia force to surface Jension is known as
A. Mach number
B. Froude number
C. Reynoldss number
D. Weber's number
Answer : D

11. Choose the wrong statement
A. The horizontal component of the hydrostatic force on any surface is equal to the normal force on the vertical projection of the surface
B. The horizontal component acts through the center of pressure for the vertical projection
C. The vertical component of the hydrostatic force on any surface is equal to the weight of the volume of the liquid above the area
D. The vertical component passes through the center of pressure of the volume
Answer : D

12. 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

13. Coefficient of contraction is the ratio of
A. Actual velocity of jet at vena contracta to the theoretical velocity
B. Loss of head in the orifice to the head of water available at the exit of the orifice
C. Loss of head in the orifice to the head of water available at the exit of the orifice
D. Area of jet at vena-contracta to the area of orifice
Answer : D

14. The surface tension of mercury at normal temperature compared to that of water is
A. More
B. Less
C. Same
D. More or less depending on size of glass tube
Answer : A

15. The flow in a pipe or channel is said to be non-uniform when
A. The liquid particles at all sections have the same velocities
B. The liquid particles at different sections have different velocities
C. The quantity of liquid flowing per second is constant
D. Each liquid particle has a definite path
Answer : B

16. 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

17. The coefficient of venturi-flume, generally, lies between
A. 0.3 to 0.45
B. 0.50 to 0.75
C. 0.75 to 0.95
D. 0.95 to 1.0
Answer : D

18. A body floats in stable equilibrium
A. When its meatcentric height is zero
B. When the metacentre is above C.G.
C. When its e.g. is below its center of buoyancy
D. Metacentre has nothing to do with position of e.g. for determining stability
Answer : B

19. The pressure of a liquid measured with the help of a Piezometer tube is
A. Vacuum pressure
B. Gauge pressure
C. Absolute pressure
D. Atmospheric pressure
Answer : B

20. Liquids
A. Cannot be compressed
B. Occupy definite volume
C. Are not affected by change in pressure and temperature
D. None of the above
Answer : D

21. The pressure of the liquid flowing throug the divergent portion of a Venturimeter
A. Remains constant
B. Increases
C. Decreases
D. Depends upon mass of liquid
Answer : C

22. In one dimensional flow, the flow
A. Is steady and uniform
B. Takes place in straight line
C. Takes place in curve
D. Takes place in one direction
Answer : B

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

24. 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

25. For a body floating in a liquid the normal pressure exerted by the liquid acts at
A. Bottom surface of the body
B. C.G. of the body
C. Metacentre
D. All points on the surface of the body
Answer : D

26. A glass tube of small diameter (d) is dipped in fluid. The height of rise or fall in the tube given by (where w = Specific weight of liquid, ? = Angle of contact of the liquid surface, and ? = Surface tension)
A. 4wd/? cos?
B. ? cos?/4wd
C. 4? cos?/wd
D. wd/4? cos?
Answer : C

27. In a footstep bearing, if the speed of the shaft is doubled, then the torque required to overcome the viscous resistance will be
A. Double
B. Four times
C. Eight times
D. Sixteen times
Answer : A

28. The torque required to overcome viscous resistance of a footstep bearing is (where ? = Viscosity of the oil, N = Speed of the shaft, R = Radius of the shaft, and t = Thickness of the oil film)
A. ??²NR/60t
B. ??²NR²/60t
C. ??²NR³/60t
D. ??²NR?/60t
Answer : D

29. The velocity at which the flow changes from laminar flow to turbulent flow is called
A. Critical velocity
B. Velocity of approach
C. Sub-sonic velocity
D. Super-sonic velocity
Answer : A

30. 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

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

32. The shear stress between the two liquid layers is __________ proportional to the distance between two layers.
A. Directly
B. Inversely
C. Both A and B
D. None of these
Answer : B

33. The line of action of the buoyant force acts through the Centroid of the
A. Submerged body
B. Volume of the floating body
C. Volume of the fluid vertically above the body
D. Displaced volume of the fluid
Answer : D

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

35. Which of the following is the unit of kinematic viscosity?
A. Pascal
B. Poise
C. Stoke
D. Faraday
Answer : C

36. The center of pressure of a surface subjected to fluid pressure is the point
A. On the surface at which resultant pressure acts
B. On the surface at which gravitational force acts
C. At which all hydraulic forces meet
D. Similar to metacentre
Answer : A

37. 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

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

39. The shear stress-strain graph for a Newtonian fluid is a
A. Straight line
B. Parabolic curve
C. Hyperbolic curve
D. Elliptical
Answer : A

40. The value of mass density in kg-sec-V-m? for water at 0°C is
A. 1
B. 1000
C. 100
D. 101.9
Answer : D

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

42. Mercury is often used in barometer because
A. It is the best liquid
B. The height of barometer will be less
C. Its vapour pressure is so low that it may be neglected
D. Both (B) and (C)
Answer : D

43. The fluid forces considered in the Navier Stokes equation are
A. Gravity, pressure and viscous
B. Gravity, pressure and turbulent
C. Pressure, viscous and turbulent
D. Gravity, viscous and turbulent
Answer : A

44. A manometer is used to measure
A. Low pressure
B. Moderate pressure
C. High pressure
D. Atmospheric pressure
Answer : C

45. The unit of kinematic viscosity in S. I. units is
A. N-m/s
B. N-s/m²
C. m²/s
D. N-m
Answer : C

46. A piece of wood having weight 5 kg floats in water with 60% of its volume under the liquid. The specific gravity of wood is
A. 0.83
B. 0.6
C. 0.4
D. 0.3
Answer : B

47. 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

48. To avoid vaporisation in the pipe line, the pipe line over the ridge is laid such that it is not more than
A. 2.4 m above the hydraulic gradient
B. 6.4 m above the hydraulic gradient
C. 10.0 m above the hydraulic gradient
D. 5.0 above the hydraulic gradient
Answer : B

49. The water pressure per metre length on a vertical masonry wall of dam is (where w = Specific weight of the liquid, and H = Height of the liquid)
A. wH/2
B. wH
C. wH²/2
D. wH²/4
Answer : C

50. 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