# Fluid Mechanics MCQ Mechanical Engineering

50 Questions 30 Mins

### 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

• Newton
• Gram
• Pascal
• Pound

### 3. 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

### 4. The specific volume of a liquid is the reciprocal of

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

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

### 6. Stoke is the unit of

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

### 7. The pressure less than atmospheric pressure is known as

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

### 8. 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

### 9. 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

### 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

• pascal
• grams
• milliters
• meters

• Pa-s
• N-s/m2
• Poise
• Stokes

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

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

### 15. The value of the compressibility of an ideal fluid is

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

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

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

### 17. 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

### 18. The value of the viscosity of an ideal fluid is

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

• zero
• unity
• infinity
• very low

### 20. Buoyant force is equal to

• upward pressure/downward pressure
• upward pressure + downward pressure
• upward pressure - downward pressure
• none of the above

### 21. Which of the following is NOT a fluid?

• carbon dioxide
• hydrogen
• seawater
• wood

### 22. The flow in a pipe is laminar when Reynold number is

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

• U-bend
• 30° bend
• 45° bend
• 90° bend

• helium
• ice
• iron
• gold

• Solid
• Liquid
• Gas
• Fluid

### 26. The rate of change of velocity due to change of position of fluid particles in a fluid flow is called as

• normal acceleration
• tangential acceleration
• convective acceleration
• local acceleration

### 27. 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

### 28. Rise of liquid in a capillary tube is due to

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

### 29. 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

### 30. If there is bucket full of oil and bucket full of water and you are asked to lift them, which one of the two will require more effort given that volume of buckets remains same?

• Oil bucket
• Water bucket
• Equal effort will be required to lift both of them
• None of the mentioned

### 31. The fluid will rise in capillary when the capillary is placed in fluid, if

• the adhesion force between molecules of fluid and tube is less than the cohesion between liquid molecules
• the adhesion force between molecules of fluid and tube is more than the cohesion between liquid molecules
• the adhesion force between molecules of fluid and tube is equal to the cohesion between liquid molecules
• None of the above

• Density
• Stress
• Strain
• Strain Rate

### 33. If a person studies about a fluid which is at rest, what will you call his domain of study?

• Fluid Mechanics
• Fluid Statics
• Fluid Kinematics
• Fluid Dynamics

### 34. Which one of the following is the wrong statement about capillarity?Magnitudes depends upon

• The diameter of tube
• The specific weight of the liquid
• Its surface tension
• Its viscosity

### 35. The velocity vector in a fluid flow is given by, V=4x3i-10x2yj+2tk.Find the velocity vector of a fluid particle at (2,1,3) at t=1

• 32i + 40 j-2k
• 32i-40j-2k
• 32i-40j+2k
• -32i+40j+2k

### 36. 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

### 37. 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

### 38. The coefficient of discharge for an external mouthpiece depends upon

• velocity of liquid
• pressure of liquid
• area of mouthpiece
• length of mouthpiece

### 39. While starting a centrifugal pump, its delivery valve should be kept

• Opened
• Closed
• Either opened or closed ; it does not make any difference
• Either opened or closed; depending on the fluid viscosity

### 40. Priming of a centrifugal pump is done to

• Increase the mass flow rate of fluid
• Develop effective pressure rise by the pump
• Avoid chances of separation inside the impeller
• None of these

• 0.5 Poise
• 1 poise
• 1.5 poise
• 2 poise

• Solid
• Liquid
• Fluid
• Gaseous

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

• 30m, 0.12 m
• 30m, 0.20 m
• 20m, 0.31 m
• 20m ,0.40 m

• 4,3
• 5,4
• 6,5
• 7,6

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

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

### 47. According to Archimede's principle, if a body is immersed partially or fully in a fluid then the buoyancy force is _______ the weight of fluid displaced by the body.

• equal to
• less than
• more than
• unpredictable

### 48. 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

### 49. 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

### 50. 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