1000+ Fluid Mechanics MCQ for LSAT [Solved]

1. 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

2. The centre of pressure acts __________ the centre of gravity of immersed surface.
A. At
B. Above
C. Below
D. None of these
Answer : C

3. 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

4. A submerged body is said to be in a stable equilibrium, if its centre of gravity __________ the centre of buoyancy.
A. Coincides with
B. Lies below
C. Lies above
D. None of these
Answer : B

5. 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

6. The loss of head due to friction in a pipe of uniform diameter in which a viscous flow is taking place, is (where RN = Reynold number)
A. 1/R_N
B. 4/R_N
C. 16/R_N
D. 64/R_N
Answer : C

7. Two dimensional flows 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 : D

8. Specific weight of water in S.I. units is equal to
A. 1000 N/m³
B. 10000 N/m³
C. 9.81 × 10³ N/m³
D. 9.81 × 10? N/m³
Answer : C

9. Dynamic viscosity of most of the gases with rise in temperature
A. Increases
B. Decreases
C. Remain unaffected
D. Unpredictable
Answer : A

10. The force of buoyancy is always __________ the weight of the liquid displaced by the body.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : A

11. 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 acts at a distance __________ from the liquid surface.
A. H/3
B. H/2
C. 2H/3
D. 3H/4
Answer : C

12. 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

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

14. 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

15. The siphon will work satisfactorily, if the minimum pressure in the pipe is __________ vapour pressure of liquid.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : C

16. The hammer blow in pipes occurs when
A. There is excessive leakage in the pipe
B. The pipe bursts under high pressure of fluid
C. The flow of fluid through the pipe is suddenly brought to rest by closing of the valve
D. The flow of fluid through the pipe is gradually brought to rest by closing of the valve
Answer : C

17. Hot wire anemometer is used to measure
A. Pressure in gases
B. Liquid discharge
C. Pressure in liquids
D. Gas velocities
Answer : D

18. 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

19. One stoke is equal to
A. 10^-2 m²/s
B. 10^-3 m²/s
C. 10^-4 m²/s
D. 10^-6 m²/s
Answer : C

20. The variation in the volume of a liquid with the variation of pressure is called its
A. Surface tension
B. Compressibility
C. Capillarity
D. Viscosity
Answer : B

21. The pressure measured with the help of a pressure gauge is called
A. Atmospheric pressure
B. Gauge pressure
C. Absolute pressure
D. Mean pressure
Answer : B

22. 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

23. An open tank containing liquid is moving with an acceleration on an inclined plane. The inclination of the free surface of the liquid will be __________ to the acceleration of the tank.
A. Equal to
B. Directly proportional
C. Inversely proportional
D. None of these
Answer : B

24. The error in discharge (dQ/Q) to the error in measurement of head (dH/H) over a triangular notch is given by
A. dQ/Q = 3/2 × (dH/H)
B. dQ/Q = 2 × (dH/H)
C. dQ/Q = 5/2 × (dH/H)
D. dQ/Q = 3 × (dH/H)
Answer : C

25. 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

26. 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

27. 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

28. The time oscillation of a floating body with increase in meatcentric height will be
A. Same
B. Higher
C. Lower
D. Lower/higher depending on weight of body
Answer : C

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

30. The unit of surface tension is
A. N/m
B. N/m²
C. N/m³
D. N-m
Answer : A

31. 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

32. 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

33. A flow in which the quantity of liquid flowing per second is not constant, is called
A. Streamline flow
B. Turbulent flow
C. Steady flow
D. Unsteady flow
Answer : D

34. 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

35. When a cylindrical vessel of radius (r) containing liquid is revolved about its vertical axis ? rad/s, then depth of parabola which the liquid assumes is
A. ?.r/2g
B. ?².r²/2g
C. ?.r/4g
D. ?².r²/4g
Answer : B

36. 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

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

38. A jet of water discharging from a 40 mm diameter orifice has a diameter of 32 mm at its vena contracta. The coefficient of contraction is
A. 0.46
B. 0.64
C. 0.78
D. 0.87
Answer : B

39. During the opening of a valve in a pipe line, the flow is
A. Steady
B. Unsteady
C. Uniform
D. Laminar
Answer : B

40. Cavitation will begin when
A. The pressure at any location reaches an absolute pressure equal to the saturated vapour pressure of the liquid
B. Pressure becomes more than critical pressure
C. Flow is increased
D. Pressure is increased
Answer : A

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

42. The resultant of all normal pressures acts
A. At C.G. of body
B. At center of pressure
C. Vertically upwards
D. At metacentre
Answer : C

43. 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

44. The velocity 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 : C

45. 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

46. 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

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

48. 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

49. The Newton's law of resistance is based on the assumption that the
A. Planes of the body are completely smooth
B. Space around the body is completely filled with the fluid
C. Fluid particles do not exert any influence on one another
D. All of the above
Answer : D

50. 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