Fluid Mechanics 1000+ MCQ with answer for SSC Scientific Assistant

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

2. Choose the wrong statement
A. Fluids are capable of flowing
B. Fluids conform to the shape of the containing vessels
C. When in equilibrium, fluids cannot sustain tangential forces
D. When in equilibrium, fluids can sustain shear forces
Answer : D

3. The buoyancy depends upon the
A. Weight of the liquid displaced
B. Pressure with which the liquid is displaced
C. Viscosity of the liquid
D. Compressibility of the liquid
Answer : A

4. According to Manning's formula, the discharge through an open channel is (where M = Manning's constant)
A. A × M × m^1/2 × i^2/3
B. A × M × m^2/3 × i^1/2
C. A^1/2 × M^2/3 × m × i
D. A^2/3 × M^1/3 × m × i
Answer : B

5. In a lock-gate, the reaction between two gates is (where P = Resultant pressure on the lock gate, and ? = Inclination of the gate with the normal to the side of the lock)
A. p/sin?
B. 2p/sin?
C. p/2sin?
D. 2p/sin (?/2)
Answer : C

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

7. For manometer, a better liquid combination is one having
A. Higher surface tension
B. Lower surface tension
C. Surface tension is no criterion
D. High density and viscosity
Answer : A

8. 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

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

10. 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

11. General energy equation holds for
A. Steady flow
B. Turbulent flow
C. Laminar flow
D. Non-uniform flow
Answer : D

12. The intensity of pressure at any point, in a liquid, is
A. Directly proportional to the area of the vessel containing liquid
B. Directly proportional to the depth of liquid from the surface
C. Directly proportional to the length of the vessel containing liquid
D. Inversely proportional to the depth of liquid from the surface
Answer : B

13. The critical depth meter is used to measure
A. Velocity of flow in an open channel
B. Depth of flow in an open channel
C. Hydraulic jump
D. Depth of channel
Answer : C

14. The absolute pressure is equal to
A. Gauge pressure + atmospheric pressure
B. Gauge pressure - atmospheric pressure
C. Atmospheric pressure - gauge pressure
D. Gauge pressure - vacuum pressure
Answer : A

15. 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

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

17. Manometer 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 : A

18. The buoyancy depends on
A. Mass of liquid displaced
B. Viscosity of the liquid
C. Pressure of the liquid displaced
D. Depth of immersion
Answer : A

19. 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

20. Capillary action is due to the
A. Surface tension
B. Cohesion of the liquid
C. Adhesion of the liquid molecules and the molecules on the surface of a solid
D. All of the above
Answer : D

21. The increase of temperature results in
A. Increase in viscosity of gas
B. Increase in viscosity of liquid
C. Decrease in viscosity of gas
D. Decrease in viscosity of liquid
Answer : D

22. 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

23. 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

24. Newton's law of viscosity is a relationship between
A. Pressure, velocity and temperature
B. Shear stress and rate of shear strain
C. Shear stress and velocity
D. Rate of shear strain and temperature
Answer : B

25. A tank of uniform cross-sectional area (A) containing liquid upto height (H1) has an orifice of cross-sectional area (a) at its bottom. The time required to empty the tank completely will be
A. (2A?H?)/(C_d × a?2g)
B. (2AH?)/(C_d × a?2g)
C. (2AH?^3/2)/(C_d × a?2g)
D. (2AH?²)/(C_d × a?2g)
Answer : A

26. A nozzle placed at the end of a water pipe line discharges water at a
A. Low pressure
B. High pressure
C. Low velocity
D. High velocity
Answer : D

27. 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

28. 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

29. 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

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

31. The theoretical velocity of jet at vena contracta is (where H = Head of water at vena contracta)
A. 2gH
B. H × ?(2g)
C. 2g × ?H
D. ?(2gh)
Answer : D

32. The weight per unit volume of a liquid at a standard temperature and pressure is called
A. Specific weight
B. Mass density
C. Specific gravity
D. None of these
Answer : A

33. The height of a water column equivalent to a pressure of 0.15 MPa is
A. 15.3 m
B. 25.3 m
C. 35.3 m
D. 45.3 m
Answer : A

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

35. According to Newton's law of viscosity, the shear stress on a layer of a fluid is __________ to the rate of shear strain.
A. Equal to
B. Directly proportional
C. Inversely proportional
D. None of these
Answer : B

36. The process of diffusion of one liquid into the other through a semi permeable membrane is called
A. Viscosity
B. Osmosis
C. Surface tension
D. Cohesion
Answer : B

37. A weir, generally, used as a spillway of a dam is
A. Narrow crested weir
B. Broad crested weir
C. Ogee weir
D. Submerged weir
Answer : C

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

39. For very great pressures, viscosity of moss gases and liquids
A. Remain same
B. Increases
C. Decreases
D. Shows erratic behaviour
Answer : D

40. 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

41. 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

42. Venturimeter is used to
A. Measure the velocity of a flowing liquid
B. Measure the pressure of a flowing liquid
C. Measure the discharge of liquid flowing in a pipe
D. Measure the pressure difference of liquid flowing between two points in a pipe line
Answer : C

43. The torque required to overcome viscous resistance of a collar bearing is (where R1 andR2 = External and internal radius of collar)
A. (??²N/60t) × (R? - R?)
B. (??²N/60t) × (R?² - R?²)
C. (??²N/60t) × (R?³ - R?³)
D. (??²N/60t) × (R?? - R??)
Answer : D

44. Reynold's number is the ratio of inertia force to
A. Pressure force
B. Elastic force
C. Gravity force
D. Viscous force
Answer : D

45. Surface tension
A. Acts in the plane of the interface normal to any line in the surface
B. Is also known as capillarity
C. Is a function of the curvature of the interface
D. Decreases with fall in temperature
Answer : A

46. The total head of a liquid particle in motion is equal to
A. Pressure head + kinetic head + potential head
B. Pressure head - (kinetic head + potential head)
C. Potential head - (pressure head + kinetic head)
D. Kinetic head - (pressure head + potential head)
Answer : A

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

48. 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

49. The velocity corresponding to Reynold number of 2800, is called
A. Sub-sonic velocity
B. Super-sonic velocity
C. Lower critical velocity
D. Higher critical velocity
Answer : D

50. The most economical section of a rectangular channel is one which has hydraulic mean depth or hydraulic radius equal to
A. Half the depth
B. Half the breadth
C. Twice the depth
D. Twice the breadth
Answer : A