About Fluid Mechanics

Following are some of the multiple choice questions on the Fluid Mechanics with answers that will help the students in developing their knowledge.

Fluid Mechanics MCQ

1. Surface tension is

  • Line force
  • Force per unit surface area
  • For per unit volume
  • All the above

2. The SI unit of pressure

  • Newton
  • Gram
  • Pascal
  • Pound

3. The specific volume of a liquid is the reciprocal of

  • weight density
  • specific weight
  • specific volume
  • mass density

4. The specific gravity of a liquid has

  • the same unit as that of mass density
  • the same unit as that of weight density
  • the same unit as that of specific volume
  • no unit

5. One litre of water occupies a volume of

  • 100 cm3
  • 250 cm3
  • 500 cm3
  • 1000 cm3

6. The pressure less than atmospheric pressure is known as

  • suction pressure
  • vacuum pressure
  • negative gauge pressure
  • all of these

7. What is an ideal fluid?

  • A fluid which has no viscosity
  • A fluid which is incompressible
  • A fluid which has no surface tension
  • All of the above

8. Select the wrong statement

  • An equivalent pipe is treated as an ordinary pipe for all calculations
  • The length of an equivalent pipe is equal to that of a compound pipe
  • The discharge through an equivalent pipe is equal to that of a compound pipe
  • The diameter of an equivalent pipe is equal to that of a compound pipe

9. Stoke is the unit of

  • dynamic viscosity
  • kinematic viscosity
  • specific volume
  • specific weight

10. Continuity equation deals with the law of conservation of

  • Mass
  • Momentum
  • Energy
  • None of above

11. The kinematic viscosity is the

  • ratio of absolute viscosity to the density of the liquid
  • ratio of density of the liquid to the absolute viscosity
  • product of absolute viscosity and density of the liquid
  • product of absolute viscosity and mass of the liquid

12. What is the unit of measurement for pressure?

  • pascal
  • grams
  • milliters
  • meters

13. Which of the following contribute to the reason behind the origin of surface tension?

  • only cohesive forces
  • only adhesive forces
  • neither cohesive forces nor adhesive forces
  • both cohesive forces and adhesive forces

14. A Newtonian fluid is defined as the fluid which

  • is highly viscous
  • is compressible and non-viscous
  • is incompressible and viscous
  • obeys Newton's law of viscosity

15. Which one of the following is not a unit of dynamic viscosity?

  • Pa-s
  • N-s/m2
  • Poise
  • Stokes

16. The value of bulk modulus of a fluid is required to determine

  • Reynold's number
  • Froude's number
  • Mach number
  • Euler's number

17. How can we determine whether the flow is laminar or turbulent?

  • Reynold’s number
  • Mach number
  • Froude number
  • Knudsen number

18. Which device is popularly used for measuring difference of low pressure?

  • Inverted U-tube Differential Manometer
  • U-tube Differential Manometer
  • Inclined Single column manometer
  • Vertical Single column manometer

19. The value of the compressibility of an ideal fluid is

  • zero
  • unity
  • infinity
  • more than that of a real fluid

20. The value of the viscosity of an ideal fluid is

  • zero
  • unity
  • infinity
  • more than that of a real fluid

21. The value of the Bulk Modulus of elasticity for an incompressible fluid is

  • zero
  • unity
  • infinity
  • very low

22. Buoyant force is equal to

  • upward pressure/downward pressure
  • upward pressure + downward pressure
  • upward pressure - downward pressure

23. The flow in a pipe is laminar when Reynold number is

  • less than 2000
  • between 2000 and 4000
  • more than 4000
  • none of these

24. Which of the following is NOT a fluid?

  • carbon dioxide
  • hydrogen
  • seawater
  • wood

25. Which of the following is a fluid?

  • helium
  • ice
  • iron
  • gold

26. Rise of liquid in a capillary tube is due to

  • Cohesion
  • Adhesion
  • Both A & B
  • Neither A nor B

27. Shear stress in a fluid flowing in a round pipe

  • Varies parabolically across the cross-section
  • Remains constant over the cross-section
  • Is zero at the centre and varies linearly with the radius
  • Is zero at the wall and increases linearly to the centre

28. Which of the following is the dimension of kinematic viscosity?

  • [L1 T-1]
  • [L1 T-2]
  • [L2 T-1]
  • [L2 T-2]

29. Which of the following is the most common pump for pumping either raw sewage or sludge?

  • Electromagnetic pump
  • Centrifugal pump
  • Reciprocating pump
  • Gear pump

30. Purpose of relief valve in a reciprocating pump is to

  • Protect the pump against developing excessive pressure
  • Facilitate unidirectional flow of liquid
  • Reduce the discharge pressure
  • Control the rate of discharge

31. Reciprocating pumps compared to centrifugal pumps

  • Deliver liquid at uniform pressure
  • Can handle slurries more efficiently
  • Are not subject to air binding
  • Can be operated with delivery valve closed

32. Helium balloons rise on earth because

  • helium is less dense than air
  • helium is more dense than air
  • helium is cooler than air
  • helium is warmer than air

33. What is the measuring unit for mass?

  • centimeter 
  • millimeter 
  • grams 
  • pounds

34. Which units of measurement are used for volume?

  • grams
  • centimeters
  • grams/milliliter
  • milliliter

35. Put the liquids in order from most dense to least dense?

  • 4, 3, 2, 1
  • 1, 2, 3, 4
  • 3, 4, 2, 1, 
  • 4, 3, 1, 2

36. What units are used to measure Density?

  • cm3/g
  • g
  • g/cm3
  • cm3

37. Which of the following is NOT an example of laminar flow?

  • a river moving slowly in a straight line
  • smoke rising upward in a smooth column through air
  • water flowing evenly from a slight opened faucet
  • smoke twisting as it moves upward from a fire

38. What is the principle of flotation?

  • floating objects displace a fluid equal to the weight of the fluid displaced
  • floating objects displace a fluid equal to their own weight
  • floating objects exert an upward buoyant force

39. Cavitation in a centrifugal pump can be avoided by keeping the

  • Inlet pressure high
  • Outlet pressure low
  • Inlet pressure low
  • Outlet pressure high

40. Cavitation in a centrifugal pump results from

  • High discharge pressure
  • Low barometric pressure
  • High discharge velocity
  • High discharge rate

41. What is the greatest benefit of using hydraulics?

  • The multiplication of speed
  • The multiplication of operating time
  • The multiplication of fuel efficiency
  • The multiplication of force

42. What is the pressure in the hydraulic fluid?

  • 1210 N
  • 484 N/m2
  • 8000 N
  • 3025 N/m2

43. Function of air vessel provided in a reciprocating pump is to

  • Reduce discharge fluctuation
  • Reduce the danger of cavitation
  • Avoid the necessity of priming
  • Increase the pump efficiency

44. How does a liquid differ from a gas?

  • a liquid has both definite shape and definite volume, whereas a gas has neither
  • a liquid has a definite volume, unlike a gas
  • a liquid has a definite volume unlike a  gas
  • a liquid has a definite shape whereas a gas has a definite volume

45. The device used to measure the fluid pressure is _____________

  • Hygrometer
  • Calorimeter
  • Manometer
  • Thermometer

46. The velocity components in x ,y and z directions of a velocity potential function is given by,

  • u=∂Φ/∂x, v=∂Φ/∂y,w=∂Φ/∂z
  • u=-∂Φ/∂x, v=∂Φ/∂y, w= -∂Φ/∂z
  • u=-∂Φ/∂x, v= -∂Φ/∂y,w= -∂Φ/∂z
  • u =∂Φ/∂x, v= -∂Φ/∂y,w=∂Φ/∂z

47. An object weighing 500 Newtons on land is placed in water. It then weighs 450 Newtons. What is the buoyant force?

  • 50 N
  • 250 N
  • 450 N
  • 500 N

48. An object will NOT sink if its weight is ______ ______ _____ ______ ______ the buoyant force.

  • Less than or equal to
  • Greater than or equal to
  • Similar to and almost equal
  • Different from and almost equal

49. A system that multiplies force by transmitting pressure from a small surface area through a confined fluid to a larger surface area.

  • hydraulic system
  • archimedes system
  • pressure system
  • bernoulli effect

50. Applying a pressure drop across a capillary results in a volumetric flow rate 'Q' under laminar flow conditions. The flow rate for the same pressure drop, in a capillary of the same length but half the radius is

  • Q/2
  • Q/4
  • Q/8
  • Q/16

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