RRB Group D - Fluid Mechanics 1000+ MCQ [Solved] PDF Download

1. In an internal mouthpiece, if the jet after contraction does not touch the sides of the mouthpiece, then the mouthpiece is said to be
A. Running full
B. Running free
C. Partially running full
D. Partially running free
Answer : B

2. The discharge over the trapezoidal notch is equal to the discharge over the rectangular notch __________ the discharge over the triangular notch.
A. Plus
B. Minus
C. Divide
D. None of these
Answer : A

3. 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

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. For a floating body to be in equilibrium
A. Meta centre should be above e.g.
B. Centre of buoyancy and e.g. must lie on same vertical plane
C. A righting couple should be formed
D. All of the above
Answer : D

6. 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

7. 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

8. A compound pipe is required to be replaced by a new pipe. The two pipes are said to be equivalent, if
A. Length of both the pipes is same
B. Diameter of both the pipes is same
C. Loss of head and discharge of both the pipes is same
D. Loss of head and velocity of flow in both the pipes is same
Answer : C

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

10. The velocity at which the laminar flow stops, is known as
A. Velocity of approach
B. Lower critical velocity
C. Higher critical velocity
D. None of these
Answer : B

11. The total energy line lies over the centre line of the pipe by an amount equal to
A. Pressure head
B. Velocity head
C. Pressure head + velocity head
D. Pressure head - velocity head
Answer : C

12. The power transmitted through the nozzle is maximum when the head lost due to friction in the pipe is __________ of the total supply head.
A. One-half
B. One-third
C. Two-third
D. None of these
Answer : B

13. Center of buoyancy is the
A. Centroid of the displaced volume of fluid
B. Center of pressure of displaced volume
C. Does not exist
D. None of the above
Answer : A

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

15. The purpose of a surge tank is
A. To control the pressure variations due to rapid changes in the pipe line flow
B. To eliminate water hammer possibilities
C. To regulate flow of water to turbines by providing necessary retarding head of water
D. All of the above
Answer : D

16. 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

17. 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

18. Viscous force is the __________ of shear stress due to viscosity and cross-section area of flow.
A. Sum
B. Different
C. Product
D. Ratio
Answer : C

19. The line of action of the buoyant force acts through the
A. Centroid of the volume of fluid vertically above the body
B. Centre of the volume of floating body
C. Center of gravity of any submerged body
D. Centroid of the displaced volume of fluid
Answer : D

20. An open vessel of water is accelerated up an inclined plane. The free water surface will
A. Be horizontal
B. Make an angle in direction of inclination of inclined plane
C. Make an angle in opposite direction to inclination of inclined plane
D. Any one of above is possible
Answer : C

21. 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

22. For measuring flow by a Venturimeter, if should be installed in
A. Vertical line
B. Horizontal line
C. Inclined line with flow downward
D. In any direction and in any location
Answer : D

23. The discharge through an external mouthpiece is given by (where a = Cross-sectional area of the mouthpiece, and H = Height of liquid above the mouthpiece)
A. 0.855 a.?(2gH)
B. 1.855 aH.?(2g)
C. 1.585 a.?(2gH)
D. 5.85 aH.?(2g)
Answer : A

24. 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

25. 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

26. Surface tension has the units of
A. Newton-sec/m
B. Newton-m/sec
C. Newton/m
D. Newton
Answer : C

27. If cohesion between molecules of a fluid is greater than adhesion between fluid and glass, then the free level of fluid in a dipped glass tube will be
A. Higher than the surface of liquid
B. The same as the surface of liquid
C. Lower than the surface of liquid
D. Unpredictable
Answer : C

28. 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

29. A large Reynold number is indication of
A. Smooth and streamline flow
B. Laminar flow
C. Steady flow
D. Highly turbulent flow
Answer : D

30. 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

31. The mercury does not wet the glass. This is due to the property of the liquid known as
A. Cohesion
B. Adhesion
C. Viscosity
D. Surface tension
Answer : D

32. Falling drops of water become spheres due to the property of
A. Surface tension of water
B. Compressibility of water
C. Capillarity of water
D. Viscosity of water
Answer : A

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

34. When a body is placed over a liquid, it will float if
A. Gravitational force is equal to the up-thrust of the liquid
B. Gravitational force is less than the up-thrust of the liquid
C. Gravitational force is more than the up-thrust of the liquid
D. None of the above
Answer : B

35. A perfect gas
A. Has constant viscosity
B. Has zero viscosity
C. Is in compressible
D. None of the above
Answer : D

36. 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

37. 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

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

39. 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

40. 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

41. A vessel of 4 m³ contains oil which weighs 30 kN. The specific weight of the oil is
A. 4.5 kN/m³
B. 6 kN/m³
C. 7.5 kN/m³
D. 10 kN/m³
Answer : C

42. Steady flow 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 : B

43. 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

44. In order that flow takes place between two points in a pipeline, the differential pressure between these points must be more than
A. Frictional force
B. Viscosity
C. Surface friction
D. All of the above
Answer : D

45. 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

46. 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

47. Choose the wrong statement. Alcohol is used in manometer, because
A. Its vapour pressure is low
B. It provides suitable meniscus for the inclined tube
C. Its density is less
D. It provides longer length for a given pressure difference
Answer : A

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

49. 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

50. The pressure of fluid due to hammer blow is
A. Directly proportional to density of fluid
B. Inversely proportional to density of fluid
C. Directly proportional to (density)^1/2 of fluid
D. Inversely proportional to (density)^1/2 of fluid
Answer : C