# Hydraulics and Fluid Mechanics MCQ Civil Engineering

50 Questions 30 Mins

### About Hydraulics and Fluid Mechanics

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

## Hydraulics and Fluid Mechanics MCQ

### 1. Newton’s law of viscosity is a relationship between

• shear stress anctthejiate of angular distortion
• shear stress and viscosity
• shear stress, velocity and viscosity
• pressure, velocity and viscosity

### 2. An ideal fluid is

• one which obeys Newton’s law of viscosity
• frictionless and incompressible
• very viscous
• frictionless and compressible

### 3. The surface tension of mercury at normal temperature compared to that of water is

• more
• less
• same
• more or less depending on size of glass tube

### 4. Non uniform flow occurs when

• the direction and magnitude of the velocity at all points are identical
• the velocity of successive fluid par-ticles, at any point, is the same at suc-cessive periods of time
• the fluid particles move in plane or parallel planes and the streamline pat-terns are identical in each plane
• velocity, depth, pressure, etc. change from point to point in the fluid flow.

• pressure
• flow
• shape
• volume

### 6. Surface energy per unit area of a surface is numerically equal to

• atmospheric pressure
• surface tension
• force of cohesion

### 7. Flow of water in a pipe about 3 meters in diameter can be measured by

• orifice plate
• venturi
• rotameter
• pitot tube

### 8. Free surface of a liquid tends to contract to the smallest possible area due to force of

• surface tension
• viscosity
• friction
• cohesion

### 9. Buoyant force is

• resultant force acting on a floating body
• equal to the volume of liquid displaced
• the resultant force on a body due to the fluid surrounding it
• force necessary to keep a body in equilibrium

### 10. Alcohol is used in manometers because

• it has low vapour pressure
• it is clearly visible
• it has low surface tension
• it can provide longer column due to low density

### 11. A perfect gas

• has constant viscosity
• is incompressible
• is of theoretical interest
• none of the above.

### 12. When a body floating in a liquid, is displaced slightly, it oscillates about

• e.g. of body
• metacentre
• center of buoyancy
• metacentre

### 13. Mercury is often used in barometer because

• it is the best liquid
• the height of barometer will be less
• its vapour pressure is so low that it may be neglected
• both (B) and (C)

• gas law
• Boyle’s law
• Charle’s law
• Pascal’s law

### 15. Pressure of the order of 10''' torr can be measured by

• Bourdon tube
• Pirani Gauge
• micro-manometer
• ionisastion gauge

### 16. Metacentric height is given as the distance between

• the center of gravity of the body andthe meta center
• the center of gravity of the body and the center of buoyancy
• the center of gravity of the body and the center of pressure
• center of buoyancy and metacentre

• 1/3
• 1/4
• 1/2
• 2/3

• 1/2
• 2/3
• 3/2
• 2

### 19. Specific weight of sea water is more that of pure water because it contains

• dissolved air
• dissolved salt
• suspended matter
• all of the above

• 1.00
• 0.855
• 0.7H
• 0.611

### 21. Resultant pressure of the liquid in the case of an immersed body acts through

• center of gravity
• center of pressure
• metacentre
• center of buoyancy

### 22. For a floating body to be in equilibrium

• meta center should be above e.g.
• center of buoyancy and e.g. must lie on same vertical plane
• a righting couple should be formed
• all of the above

### 23. In which of the following the friction drag is generally larger than pressure drag?

• a circular disc or plate held normal to flow
• a sphere
• a cylinder
• an airfoil

### 24. The resultant of all normal pressures acts

• at e.g. of body
• at center of pressure
• vertically upwards
• at metacentre

• 1 Pa
• 91 Pa
• 981 Pa
• 9810 Pa

### 26. The normal stress is same in all directions at a point in a fluid

• only when the fluid is frictionless
• only when the fluid is incompressible and has zero viscosity
• when there is no motion of one fluid layer relative to an adjacent layer
• irrespective of the motion of one fluid layer relative to an adjacent layer

### 27. The continuity equation pi V,A,= p2V2A2 is based on the following assumption regarding flow of fluid (where pi and p2 are mass densities.)

• uniform flow
• incompressible flow
• frictionless flow

### 28. According to Bernoulli’s equation for steady ideal fluid flow

• principle of conservation of mass holds
• velocity and pressure are inversely proportional
• total energy is constant throughout
• the energy is constant along a stream-line but may vary across streamlines

### 29. A liquid compressed in cylinder has a volume of 0.04 m3 at 50 kg/cm² and a volume of 0.039 m3 at 150 kg/cm². The bulk modulus of elasticity of liquid is

• 400 kg/cm²
• 4000 kg/cm²
• 40 x 105 kg/cm²
• 40 x 106 kg/cm²

### 30. An open vessel of water is accelerated up an inclined plane. The free water surface will

• be horizontal
• make an angle in direction of inclination of inclined plane
• make an angle in opposite direction to inclination of inclined plane
• any one of above is possible

• g/3
• g/2
• 2g/3
• g

### 32. At the centre line of a pipe flowing under pressure where the velocity gradient is zero, the shear stress will be

• minimum
• maximum
• negative value
• could be any value

### 33. Choose the wrong statement.Alcohol is used in manometer, because

• its vapour pressure is low
• it provides suitable meniscus for the inclined tube
• its density is less
• it provides longer length for a given pressure difference

### 34. A bucket of water is hanging from a spring balance. An iron piece is suspended into water without touching sides of bucket from another support. The spring balance reading will

• increase
• decrease
• remain same
• increase/decrease depending on depth of immersion

### 35. For a floating body to be in stable equilibrium, its metacentre should be

• below the center of buoyancy
• above the center of buoyancy
• between e.g. and center of pressure
• above the center of gravity.

### 36. If 850 kg liquid occupies volume of one cubic meter, men 0.85 represents its

• specific weight
• specific mass
• specific gravity
• specific density

• H1/2
• H3/2
• H5/2
• H

### 38. True one-dimensional flow occurs when

• the direction and magnitude of the veiocity at all points are identical
• the velocity of successive fluid par-ticles, at any point, is the same at suc-cessive periods of time
• the magnitude and direction of the velocity do not change from point to point in the fluid
• the fluid particles move in plane or parallel planes and the streamline pat-terns are identical in each plane

### 39. The total pressure force on a plane area is equal to the area multiplied by the intensity of pressure at the centriod, if

• the area is horizontal
• the area is vertical
• the area is inclined
• all of the above

### 40. If a sphere of diameter 1 cm falls in castor oil of kinematic viscosity 10 stokes, with a terminal velocity of 1.5 cm/sec, the coefficient of drag on the sphere is

• less than 1
• between 1 and 100
• 160
• 200

### 41. The units of viscosity are

• metre2/sec
• kg sec/metre
• newton-sec/metre2
• newton-sec/metre

### 42. The discharge through a V- notch varies as

• H1/2
• H3’2
• H5/2
• H5’4 where H is head.

### 43. The Prartdtl mixing length is

• zero at the pipe wall
• maximum at the pipe wall
• independent of shear stress
• none of the above

### 44. To avoid vaporisation in the pipe line, the pipe line over the ridge is laid such that it is not more than

• 2.4 m above the hydraulic gradient
• 6.4 m above the hydraulic gradient
• 10.0 m above the hydraulic gradient
• 5.0 above the hydraulic gradient

### 45. The peoperty by virtue of which a liquid opposes relative motion between its different layers is called

• surface tension
• co-efficient of viscosity
• viscosity
• osmosis

• velocity
• discharge
• pressure

### 47. The position of center of pressure on a plane surface immersed vertically in a static mass of fluid is

• at the centroid of the submerged area
• always above the centroid of the area
• always below the centroid of the area
• none of the above

### 48. A large Roynold number is indication of

• smooth and streamline flow
• laminar flow
• turbulent flow
• highly turbulent flow.

### 49. Which of the following is demensionless

• specific weight
• specific volume
• specific speed
• specific gravity

• 0°C
• 0°K
• 4°C
• 20°C