1000+ Fluid Mechanics MCQ for CAT [Solved]

1. For a perfect incompressible liquid, flowing in a continuous stream, the total energy of a particle remains the same, while the particle moves from one point to another. This statement is called
A. Continuity equation
B. Bernoulli's equation
C. Pascal's law
D. Archimedess principle
Answer : B

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

3. Falling drops of water become spheres due to the property of
A. Adhesion
B. Cohesion
C. Surface tension
D. Viscosity
Answer : C

4. According to Francis formula, the discharge over a rectangular weir is (where n = Number of end contractions)
A. (2/3) × C_d (L - nH) × ?(2gh)
B. (2/3) × C_d (L - 0.1nH) × ?(2g) × H^3/2
C. (2/3) × C_d (L - nH) × ?(2g) × H²
D. (2/3) × C_d (L - nH) × ?(2g) × H^5/2
Answer : B

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

6. A moving fluid mass may be brought to a static equilibrium position, by applying an imaginary inertia force of the same magnitude as that of the accelerating force but in the opposite direction. This statement is called
A. Pascal's law
B. Archimedess principle
C. D-Alembert's principle
D. None of these
Answer : C

7. The horizontal component of buoyant force is
A. Negligible
B. Same as buoyant force
C. Zero
D. None of the above
Answer : C

8. 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

9. 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

10. For similarity, in addition to models being geometrically similar to prototype, the following in both cases should also be equal
A. Ratio of inertial force to force due to viscosity
B. Ratio of inertial force to force due to gravitation
C. Ratio of inertial force to force due to surface tension
D. All the four ratios of inertial force to force due to viscosity, gravitation, surface tension, and elasticity
Answer : D

11. Flow of water in a pipe about 3 metres in diameter can be measured by
A. Orifice plate
B. Venturimeter
C. Rotameter
D. Pitot tube
Answer : D

12. The ratio of the inertia force to the __________ is called Euler's number.
A. Pressure force
B. Elastic force
C. Surface tension force
D. Viscous force
Answer : A

13. 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

14. Property of a fluid by which its own molecules are attracted is called
A. Adhesion
B. Cohesion
C. Viscosity
D. Compressibility
Answer : B

15. 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

16. A fluid having no viscosity is known as
A. Real fluid
B. Ideal fluid
C. Newtonian fluid
D. Non-Newtonian fluid
Answer : B

17. If 850 kg liquid occupies volume of one cubic meter, men 0.85 represents its
A. Specific weight
B. Specific mass
C. Specific gravity
D. Specific density
Answer : C

18. The discharge through a channel of trapezoidal section is maximum when
A. Width of channel at the top is equal to twice the width at the bottom
B. Depth of channel is equal to the width at the bottom
C. The sloping side is equal to half the width at the top
D. The sloping side is equal to the width at the bottom
Answer : C

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

20. An ideal flow of any fluid must fulfil the following
A. Newton's law of motion
B. Newton's law of viscosity
C. Pascal' law
D. Continuity equation
Answer : D

21. The flow which neglects changes in a transverse direction i known as
A. One dimensional flow
B. Uniform flow
C. Steady flow
D. Turbulent flow
Answer : A

22. 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

23. The body will sink down if the force of buoyancy is __________ the weight of the liquid displaced.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : B

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

25. 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

26. The discharge through a wholly drowned orifice is given by (where H1 = Height of water (on the upstream side) above the top of the orifice, H2 = Height of water (on the downstream side) above the bottom of the orifice, and H = Difference between two water levels on either side of the orifice)
A. Q = C_d × bH? × ?(2gh)
B. Q = C_d × bH₂ × ?(2gh)
C. Q = C_d × b (H₂ - H₁) × ?(2gh)
D. Q = C_d × bH × ?(2gh)
Answer : C

27. 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

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

29. A flow is called hyper-sonic, if the Mach number is
A. Less than unity
B. Unity
C. Between 1 and 6
D. None of these
Answer : D

30. Cavitation is caused by
A. High velocity
B. High pressure
C. Weak material
D. Low pressure
Answer : D

31. The unit of viscosity is
A. Metres² per sec
B. kg-sec/metre
C. Newton-sec per metre²
D. Newton-sec per meter
Answer : B

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

33. The total pressure on an immersed surface inclined at an angle ? with the liquid surface is
A. wA
B. wx
C. wAx
D. wAx/sin?
Answer : C

34. 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

35. 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

36. A notch is used to measure __________ of liquids.
A. Pressure
B. Discharge
C. Velocity
D. Volume
Answer : B

37. The power absorbed (in watts) in overcoming the viscous resistance of a footstep bearing is
A. ? ?³ N² R² /1800 t
B. ? ?³ N² R? /1800 t
C. ? ?³ N² R² /3600 t
D. ? ?³ N² R? /3600 t
Answer : B

38. 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

39. 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

40. 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

41. 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

42. A uniform body 3 m long, 2 m wide and 1 m deep floats in water. If the depth of immersion is 0.6 m, then the weight of the body is
A. 3.53 kN
B. 33.3 kN
C. 35.3 kN
D. None of these
Answer : C

43. The length AB of a pipe ABC in which the liquid is flowing has diameter (d₁) and is suddenly contracted to diameter (d₂) at B which is constant for the length BC. The loss of head due to sudden contraction, assuming coefficient of contraction as 0.62, is
A. v?²/2g
B. v?²/2g
C. 0.5 v?²/2g
D. 0.375 v?²/2g
Answer : D

44. Kinematic viscosity is dependent upon
A. Pressure
B. Distance
C. Density
D. Flow
Answer : C

45. 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

46. The Reynold's number of a ship is __________ to its velocity and length.
A. Directly proportional
B. Inversely proportional
C. Square root of velocity
D. None of these
Answer : A

47. A pitot tube is used to measure the
A. Velocity of flow at the required point in a pipe
B. Pressure difference between two points in a pipe
C. Total pressure of liquid flowing in a pipe
D. Discharge through a pipe
Answer : A

48. Uniform flow occurs when
A. The flow is steady
B. The flow is streamline
C. Size and shape of the cross section in a particular length remain constant
D. Size and cross section change uniformly along length
Answer : C

49. 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

50. An opening in the side of a tank or vessel such that the liquid surface with the tank is below the top edge of the opening, is called
A. Weir
B. Notch
C. Orifice
D. None of these
Answer : B