1000+ Fluid Mechanics Multiple Choice Question Answer [Solved]

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. In order to increase sensitivity of U-tube manometer, one leg is usually inclined by angle ?. Sensitivity of inclined tube to sensitivity of Utube is equal to
A. Sin?
B. 1/Sin?
C. Cos?
D. 1/Cos?
Answer : B

3. 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

4. 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

5. The centre of gravity of the volume of the liquid displaced by an immersed body is called
A. Centre of gravity
B. Centre of pressure
C. Metacentre
D. Centre of buoyancy
Answer : D

6. 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

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

8. According to Bazin's formula, the discharge over a rectangular weir is mL2g x H^3/2where m is equal to
A. 0.405 + (0.003/H)
B. 0.003 + (0.405/H)
C. 0.405 + (H/0.003)
D. 0.003 + (H/0.405)
Answer : A

9. A streamline is defined as the line
A. Parallel to central axis flow
B. Parallel to outer surface of pipe
C. Of equal velocity in a flow
D. Along which the pressure drop is uniform
Answer : C

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

11. When the Mach number is less than unity, the flow is called
A. Sub-sonic flow
B. Sonic flow
C. Super-sonic flow
D. Hyper-sonic flow
Answer : A

12. 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

13. 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

14. A hydraulic press has a ram of 15 cm diameter and plunger of 1.5 cm. It is required to lift a weight of 1 tonne. The force required on plunger is equal to
A. 10 kg
B. 100 kg
C. 1000 kg
D. 1 kg
Answer : A

15. The value of bulk modulus of a fluid is required to determine
A. Reynold's number
B. Froude's number
C. Mach number
D. Euler's number
Answer : C

16. 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

17. To avoid vaporisation in the pipe line, the pipe line over the ridge is laid such that it is not more than
A. 2.4 m above the hydraulic gradient
B. 6.4 m above the hydraulic gradient
C. 10.0 m above the hydraulic gradient
D. 5.0 above the hydraulic gradient
Answer : B

18. The pressure at a point 4 m below the free surface of water is
A. 19.24 kPa
B. 29.24 kPa
C. 39.24 kPa
D. 49.24 kPa
Answer : C

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

20. Which of the following instrument can be used for measuring speed of a submarine moving in deep sea?
A. Venturimeter
B. Orifice plate
C. Hot wire anemometer
D. Pitot tube
Answer : D

21. The maximum discharge over a broad crested weir is
A. 0.384 C_d × L × H^1/2
B. 0.384 C_d × L × H^3/2
C. 1.71 C_d × L × H^1/2
D. 1.71 C_d × L × H^3/2
Answer : D

22. If the coefficient of discharge is 0.6, then the discharge over a right angled notch is
A. 0.417 H^5/2
B. 1.417 H^5/2
C. 4.171 H^5/2
D. 7.141 H^5/2
Answer : B

23. 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

24. 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

25. The bulk modulus of elasticity with increase in pressure
A. Increases
B. Decreases
C. Remain constant
D. Increases first up to certain limit and then decreases
Answer : A

26. 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

27. The difference of pressure between the inside and outside of a liquid drop is
A. p = T × r
B. p = T/r
C. p = T/2r
D. p = 2T/r
Answer : D

28. The surface tension of mercury at normal temperature is __________ that of water.
A. Same as
B. Lower than
C. Higher than
D. None of these
Answer : C

29. The pressure less than atmospheric pressure is known as
A. Suction pressure
B. Vacuum pressure
C. Negative gauge pressure
D. All of these
Answer : D

30. 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

31. 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

32. 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

33. A flow through a long pipe at constant rate is called
A. Steady uniform flow
B. Steady non-uniform flow
C. Unsteady uniform flow
D. Unsteady non-uniform flow
Answer : A

34. 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

35. The water pressure per metre length on a vertical masonry wall of dam is (where w = Specific weight of the liquid, and H = Height of the liquid)
A. wH/2
B. wH
C. wH²/2
D. wH²/4
Answer : C

36. A weir is said to be narrow-crested weir, if the width of the crest of the weir is __________ half the height of water above the weir crest.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : B

37. The specific gravity of water is taken as
A. 0.001
B. 0.01
C. 0.1
D. 1
Answer : D

38. Buoyant force is
A. Resultant force acting on a floating body
B. Equal to the volume of liquid displaced
C. Force necessary to keep a body in equilibrium
D. The resultant force on a body due to the fluid surrounding it
Answer : D

39. A vertical wall is subjected to a pressure due to one kind of liquid, on one of its sides. Which of the following statement is correct?
A. The pressure on the wall at the liquid level is minimum
B. The pressure on the bottom of the wall is maximum
C. The pressure on the wall at the liquid level is zero, and on the bottom of the wall is maximum
D. The pressure on the bottom of the wall is zer
Answer : C

40. 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

41. Metacentre is the point of intersection of
A. Vertical upward force through e.g. of body and center line of body
B. Buoyant force and the center line of body
C. Midpoint between e.g. and center of buoyancy
D. All of the above
Answer : B

42. Center of pressure compared to e.g. is
A. Above it
B. Below it
C. At same point
D. Above or below depending on area of body
Answer : B

43. Which of the following instrument can be used for measuring speed of an aeroplane?
A. Venturimeter
B. Orifice plate
C. Pitot tube
D.Answer : C

44. In a depressed nappe
A. The pressure below the nappe is atmospheric
B. The pressure below the nappe is negative
C. The pressure above the nappe is atmospheric
D. The pressure above the nappe is negative
Answer : B

45. The flow in a pipe or channel is said to be 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 : A

46. The pressure intensity in kN/m2 (or kPa) at any point in a liquid is (where w = Specific weight of liquid, and h = Depth of liquid from the surface)
A. w
B. wh
C. w/h
D. h/w
Answer : B

47. The specific weight of water is 1000 kg/m3
A. At normal pressure of 760 mm
B. At 4°C temperature
C. At mean sea level
D. All the above
Answer : D

48. A water tank contains 1.3 m deep water. The pressure exerted by the water per metre length of the tank is
A. 2.89 kN
B. 8.29 kN
C. 9.28 kN
D. 28.9 kN
Answer : B

49. 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

50. 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