Fluid Mechanics MCQ Solved Paper for SSC GD

1. 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

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

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

4. 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

5. Select the correct statement
A. Weber's number is the ratio of inertia force to elastic force.
B. Weber's number is the ratio of gravity force to surface tension force.
C. Weber's number is the ratio of viscous force to pressure force.
D. Weber's number is the ratio of inertia force to surface tension force.
Answer : D

6. 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

7. The discharge in an open channel corresponding to critical depth is
A. Zero
B. Minimum
C. Maximum
D. None of these
Answer : C

8. 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

9. Free surface of a liquid tends to contract to the smallest possible area due to force of
A. Surface tension
B. Viscosity
C. Friction
D. Cohesion
Answer : A

10. 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

11. The rise of liquid along the walls of a revolving cylinder about the initial level is __________ the depression of the liquid at the axis of rotation.
A. Same as
B. Less than
C. More than
D. None of these
Answer : A

12. 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

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

14. 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

15. 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

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

17. 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

18. The velocity of jet of water travelling out of opening in a tank filled with water is proportional to
A. Head of water (h)
B. h²
C. V/T
D. h/2
Answer : C

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

20. 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

21. 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

22. 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

23. 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

24. The viscosity of water at 20°C is
A. One stoke
B. One centistoke
C. One poise
D. One centipoise
Answer : D

25. The pressure at a point in a fluid will not be same in all the directions when the fluid is
A. Moving
B. Viscous
C. Viscous and static
D. Viscous and moving
Answer : D

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

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

28. Which of the following statement is correct?
A. In a compressible flow, the volume of the flowing liquid changes during the flow
B. A flow, in which the volume of the flowing liquid does not change, is called incompressible flow
C. When the particles rotate about their own axes while flowing, the flow is said to be rotational flow
D. All of the above
Answer : D

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

30. 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

31. Piezometer is used to measure
A. Pressure in pipe, channels etc.
B. Atmospheric pressure
C. Very low pressures
D. Difference of pressure between two points
Answer : C

32. The velocity of the liquid flowing through the divergent portion of a Venturimeter
A. Remains constant
B. Increases
C. Decreases
D. Depends upon mass of liquid
Answer : C

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

34. The loss of head at exit of a pipe is (where v = Velocity of liquid in the pipe)
A. v²/2g
B. 0.5v²/2g
C. 0.375v²/2g
D. 0.75v²/2g
Answer : A

35. Buoyant force is
A. The resultant force acting on a floating body
B. The resultant force on a body due to the fluid surrounding it
C. Equal to the volume of liquid displaced
D. The force necessary to maintain equilibrium of a submerged body
Answer : B

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

37. 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

38. In a venturi-flume, the flow takes place at
A. Atmospheric pressure
B. Gauge pressure
C. Absolute pressure
D. None of these
Answer : A

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

40. 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

41. When a body, floating in a liquid, is given a small angular displacement, it starts oscillating about a point known as
A. Centre of pressure
B. Centre of gravity
C. Centre of buoyancy
D. Metacentre
Answer : D

42. The length AB of a pipe ABC in which the liquid is flowing has diameter (d1) and is suddenly enlarged to diameter (d2) at B which is constant for the length BC. The loss of head due to sudden enlargement is
A. (v? - v?)²/g
B. (v?² - v?²)/g
C. (v? - v?)²/2g
D. (v?² - v?²)/2g
Answer : C

43. 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

44. A flow is called sub-sonic, if the Mach number is
A. Less than unity
B. Unity
C. Between 1 and 6
D. More than 6
Answer : A

45. In order to measure the flow with a Venturimeter, it is installed in
A. Horizontal line
B. Inclined line with flow upwards
C. Inclined line with flow downwards
D. Any direction and in any location
Answer : D

46. 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

47. 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

48. 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

49. Two pipe systems can be said to be equivalent, when the following quantities are same
A. Friction loss and flow
B. Length and diameter
C. Flow and length
D. Friction factor and diameter
Answer : A

50. An air vessel is provided at the summit in a siphon to
A. Avoid interruption in the flow
B. Increase discharge
C. Increase velocity
D. Maintain pressure difference
Answer : A