Hydraulics and Fluid Mechanics MCQ Civil Engineering

50 Questions 30 Mins

Fluid Mechanics: The Science of Hydraulics

Hydraulics is the study of liquids and their mechanical effects. This includes the motion of fluids and the forces exerted by them. Hydraulic systems are widely used in engineering, manufacturing, and many other industries. In this write-up, we will discuss the basics of hydraulics and fluid mechanics. We will explore how these principles are used in real-world applications.

Applications: Hydraulics is used in a variety of industries and applications. One of the most common uses is in hydraulic machinery. Hydraulic machines use fluid power to perform various tasks. Hydraulic presses, for example, use fluid power to apply pressure to an object. This pressure can be used to crush, cut, or shape the object. Hydraulics is also used in many automotive applications. Hydraulic brakes, for example, use fluid power to stop a vehicle. Hydraulic systems are also used in construction equipment, such as excavators and bulldozers. These machines use fluid power to move their large blades and buckets.

Fluid Mechanics: Fluid mechanics is a branch of physics that helps us to understand how liquids behave. It is also used in many engineering applications. One of the most important concepts in fluid mechanics is fluid pressure. Pressure is the force exerted by a fluid on an object. The pressure of a fluid depends on its density and speed.

Hydraulics and fluid mechanics are essential for many industries and applications. These principles help us to understand how fluids behave and how to design hydraulic systems. Hydraulic systems are used in a variety of industries, such as automotive, construction, and manufacturing.

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
• none of the above

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