**Top Hydraulics & Fluid Machines Objective Questions Part – 2**

**1.Buoyant force is**

resultant force acting on a floating body

equal to the volume of liquid dis�placed

force necessary to keep a body in equi�librium

the resultant force on a body due to the fluid surrounding it

none of the above.

**ANSWER : : the resultant force on a body due to the fluid surrounding it**

**2.Metacentre is the point of intersection of**

vertical upward force through e.g. of body and centre line of body

buoyant force and the centre line of body

mid point between e.g. and centre of buoyancy

all of the above

none of the above.

**ANSWER : : buoyant force and the centre line of body**

**3.Ratio of inertia force to surface Jension is known as**

Mach number

Froude number

Reynold’s number

Weber’s number

none of the above.

**ANSWER : : Weber’s number**

**4.Resultant pressure of the liquid in the case of an immersed body acts through**

centre of gravity

centre of pressure

metacentre

centre of buoyancy

in between e.g. and centre of pressure.

**ANSWER : : centre of pressure**

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

be horizontal

make an angle in direction of inclina�tion of inclined plane

make an angle in opposite direction to inclination of inclined plane

any one of above is possible

none of the above.

**ANSWER : : make an angle in opposite direction to inclination of inclined plane**

**6.When a body floating in a liquid, is displaced slightly, it oscillates about**

e.g. of body

centre of pressure

centre of buoyancy

metacentre

liquid surface.

**ANSWER : : metacentre**

**7.The two important forces for a floating body are**

buoyancy, gravity

buoyancy, pressure

buoyancy, inertial

inertial, gravity

gravity, pressure.

**ANSWER : : buoyancy, gravity**

**8.A model of a reservior is drained in 4 mts by opening the sluice gate. The model scale is 1: 225. How long should it take to empty the prototype ?**

900 minutes

4 minutes

4 x (225)3/2 minutes

4 (225)1/3 minutes

4 x V225 minutes.

**ANSWER : : 4 x V225 minutes.**

**9.Centre of pressure on an inclined plane is**

at the centroid

above the centroid

below the centroid

at metacentre

at centre of pressure.

**ANSWER : : below the centroid**

**10.If the atmospheric pressure on the surface of an oil tank (sp. gr. 0. is 0.2 kg/cm”, the pressure at a depth of 50 m below the oil surface will be**

2 metres of water column

3 metres of water column

5 metres of water column

6 metres of water Column

7 metres of water column.

**ANSWER : : 6 metres of water Column**

**11.Ratio of inertia force to elastic force is known as**

Mach number

Froude number

Reynold’s number

Weber’s number

none of the above.

**ANSWER : : Mach number**

**12.According to the principle of buoyancy a body totally or partially immersed in a fluid will be lifted up by a force equal to**

the weight of the body

more than the weight of the body

less than the weight of the body

weight of the fluid displaced by the body

weight of body plus the weight of the fluid displaced hy the body.

**ANSWER : : weight of the fluid displaced by the body**

**13.The centre of gravity of the volume of the liquid displaced by an immersed body is called**

centre of gravity

centre of pressure

metacentre

centre of buoyancy

centroid.

**ANSWER : : centre of buoyancy**

**14.For a floating body to be in stable equilibrium, its metacentre should be**

below the centre of gravity

below the centre of buoyancy

above the centre of buoyancy

between e.g. and centre of pressure

above the centre of gravity.

**ANSWER : : above the centre of gravity.**

**15.For a body floating in a liquid the normal pressure exerted by the liquid acts at**

bottom surface of the body

e.g. of the body

metacentre

all points on the surface of the body

all of the above.

**ANSWER : : all points on the surface of the body**

**16.A square surface 3 m x 3 m lies in a vertical line in water pipe its upper edge at vater surface. The hydrostatic force on square surface is**

9,000 kg

13,500 kg

1000 kg

27,000 kg

30,000 kg.

**ANSWER : : 13,500 kg**

**17.Choose the wrong statement**

The horizontal component of the hydro-static force on any surface is equal to the normal force on the verti�cal projection of the surface

The horizontal component acts through the centre of pressure for the vertical projection

The vertical component of the hydros-tatic force on any surface is equal to the weight of the volume of the liquid above the area

he vertical component passes through the centre of pressure of the volume

Centre of pressure acts at a greater depth than centre of gravity.

**ANSWER : : he vertical component passes through the centre of pressure of the volume**

**18.The line of action of the buoyant force acts through the centroid of the**

submerged body

volume of the floating body

volume of the fluid vertically above the body

displaced volume of the fluid

none of the above.

**ANSWER : : displaced volume of the fluid**

**19.Choose the wrong statement**

The centre of buoyancy is located at the centre of gravity of the displaced liquid

For stability of a submerged body, the centre of gravity of body must lie directly below the centre of buoyancy

If e.g. and centre of buoyancy coin�cide, the submerged body must lie at neutral equilibrium for all positions

For stability of floating cylinders or spheres, the e.g. of body must lie below the centre of buoyancy

All floating bodies are stable.

**ANSWER : : All floating bodies are stable.**

**20.The df pth of the centre of pressure on a vertical rectangular gate m wide and 6 m high, when the water surface coincides with the top of the gate, is**

2.4 m

3.0 m

4.0 m

“2.5 m

5.0 m.

**ANSWER : : 3.0 m**

**21.A ship whose hull length is 100 m is to travel at 10 m/sec. For dynamic similarity, at what velocity should a 1:25 model be towed through water ?**

10 m/sec

25 m/sec

2 m/sec

50 m/sec

250 m/sec.

**ANSWER : : 2 m/sec**

**22.Hot wire anemometer is used to measure**

pressure in gases

liquid discharge

pressure in liquids

gas velocities

temperature.

**ANSWER : : gas velocities**

**23.The flow in which conditions do not change with time at any point, is known as**

one dimensional flow

uniform flow

steady flow

turbulent flow

streamline flow.

**ANSWER : : steady flow**

Explanation :

**24.Flow of water in a pipe about 3 metres in diameter can be measured by**

orifice plate

venturi

rotameter

pitot tube

nozzle

**ANSWER : : pitot tube**

**25.The flow in which the velocity vector is identical in magnitude and direction at every point, for any given instant, is known as**

one dimensional flow

uniform f^w

steady flow

turbulent flow

streamline flow.

**ANSWER : : uniform f^w**

**26.During the opening of a valve in a pipe line, the flow is**

steady

unsteady

uniform

laminar

free vortex type.

**ANSWER : : unsteady**

**27.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 magnitude aricf 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

velocity, depth, pressure, etc. change from point to point in the fluid flow.

**ANSWER : : velocity, depth, pressure, etc. change from point to point in the fluid flow.**

**28.Select the correct statement**

Local atmospheric pressure depends upon elevation of locality only

Standard atmospheric pressure is the mean local atmospheric pressure a* sea level

Local atmospheric pressure is always below standard atmospheric pressure

A barometer reads the difference be-tween local and standard atmospheric pressure

Gauge piessure is equal to atmos�pheric pressure plus instrument read�ing.

**ANSWER : : Standard atmospheric pressure is the mean local atmospheric pressure a* sea level**

**29.Steady 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 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

velocity, depth, pressure, etc. change from point to point in the fluid flow.

**ANSWER : : the velocity of successive fluid par-ticles, at any point, is the same at suc-cessive periods of time**

**30.Gradually varied flow is**

steady uniform

non-steady non-uniform

non-steady uniform

steady non-uniform

true one-dimensional.

**ANSWER : : steady non-uniform**

**31.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

velocity, depth, pressure etc. change from point to point in the fluid flow.

**ANSWER : : the direction and magnitude of the veiocity at all points are identical**

**32.The pressure in the air space above an oil (sp. gr. 0. surface in a tank is 0.1 kg/cm”. The pressure at 2.5 m below the oil surface will be**

2 metres of water column

3 metres of water column

3.5 metres of water column

4 m of water column

none of the above.

**ANSWER : : 3 metres of water column**

**33.Rotameter is a device used to measure**

absolute pressure

velocity of fluid

flow

rotation

velocity of air.

**ANSWER : : flow**

**34.For measuring flow by a venturimeter, if should be installed in**

vertical line

horizontal line

inclined line with flow downward

inclined line with upward flow\

in any direction and in any location.

**ANSWER : : in any direction and in any location.**

**35.In an immersed body, centre of pressure is**

at the centre of gravity

above the centre of gravity

below be centre of gravity

could be above or below e.g. depend�ing on density of body and liquid

unpredictable.

**ANSWER : : below be centre of gravity**

**36.Flow occurring in a pipeline when a valve is being opened is**

steady

unsteady

laminar

vortex

rotational.

**ANSWER : : unsteady**

**37.Total pressure on a lmxlm gate immersed vertically at a depth of 2 m below the free water surface will be**

1000 kg

4000 kg

2000 kg

00 kg

16000 kg.

**ANSWER : : 1000 kg**

**38.Uniform flow occurs when**

the flow is steady

the flow is streamline

size and shape of the cross section in a particular length remain constant

size and cross section change uniform�ly along length

flow occurs at constant fate.

**ANSWER : : size and shape of the cross section in a particular length remain constant**

**39.In the case of steady flow of a fluid, the acceleration of any fluid particle is**

constant

variable

zero

zero under limiting conditions

never zero.

**ANSWER : : zero**

**40.An ideal flow of any fluid must satisfy**

Pascal law

Newton’s law of viscosity

boundary layer theory

continuity equation

Bernoulli’s theorem.

**ANSWER : : continuity equation**

**41.The flow in which the particles of a fluid attain such velocities that vary from point to point in magnitude and direction as well as from instant to instant, is known as**

one dimensional flow

uniform flow

steady flow

turbulent flow

streamline flow.

**ANSWER : : turbulent flow**

**42.The flow in which each liquid particle has a definite path and their paths do not cross each other is called**

one dimensional flow

uniform flow

steady flow

turbulent flow

streamline flow.

**ANSWER : : streamline flow.**

**43.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

in case of an ideal fluid.

**ANSWER : : when there is no motion of one fluid layer relative to an adjacent layer**

**44.A piece of metal of specific gravity 7 floats in mercury of specific gravity 13.6. What fraction of its volume is under mercury ?**

0.5

0.4

0.515

0.5

none of the above.

**ANSWER : : 0.515**

**45.For pipes, laminar flow occurs when Roynolds number is**

less than 2000

between 2000 and 4000

more than 4000

less than 4000

none of the above.

**ANSWER : : less than 2000**

**46.The upper surface of a weir over which water flows is known is**

crest

nappe

sill

weir top

contracta.

**ANSWER : : sill**

**47.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

none of the above.

**ANSWER : : the energy is constant along a stream-line but may vary across streamlines**

**48.The equation of continuity holds good when the flow**

is steady

is one dimensional

velocity is uniform at all the cross sec-tions

all of the above

none of the above.

**ANSWER : : all of the above**

**49.Mach number is significant in**

supersonics, as with projectiles and jet propulsion

full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.

simultaneous motion through two fluids where there is a surface of dis-continuity, gravity force, and wave making effects, as with ship’s hulls

all of fhe above

none of the above.

**ANSWER : : supersonics, as with projectiles and jet propulsion**

**50.The fluid forces considered in the Navier Stokes equation are**

gravity, pressure and viscous

gravity, pressure and turbulent

pressure, viscous and turbulent

gravity, viscous and turbulent

none of the above.

**ANSWER : : gravity, pressure and viscous**

**51.For hypersonic flow, the Mach number is**

unity

greater than unity

greater than 2

greater than 4

greater than 10.

**ANSWER : : greater than 4**

**52.A piece of wood having weight 5 kg floats in water with 60% of its volume under the liquid. The specific gravity of wood is**

0.

0.6

0.4

0.3

none of the above.

**ANSWER : : 0.6**

**53.Froude number is significant in**

supersonics, as with projectile and jet propulsion

full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.

simultaneous motion through two fluids where there is a surface of dis-continuity, gravity forces, and wave making effect, as with ship’s hulls

all of the above

none of the above

**ANSWER : : simultaneous motion through two fluids where there is a surface of dis-continuity, gravity forces, and wave making effect, as with ship’s hulls**

**54.A large Roynold number is indication of**

smooth and streamline flow

laminar flow

steady flow

turbulent flow

highly turbulent flow.

**ANSWER : : highly turbulent flow.**

**55.Reynolds number is significant in**

supersonics, as with projectile and jet propulsion

full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.

simultaneous motion through two fluids where there is a surface of dis-continuity, gravity forces, and wave making effect, as with ship’s hulls

all of the above

none of the above.

**ANSWER : : full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.**

**56.In a free vortex motion, the radial component of velocity everywhere is**

maximum

minimum

zero

non-zero and finite

unpredictable.

**ANSWER : : zero**

**57.Two dimensional 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 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

velocity, depth, pressure, etc. change from point to point in the fluid flow.

**ANSWER : : the fluid particles move in plane or parallel planes and the streamline pat-terns are identical in each plane**

**58.Pitot tube is used for measurement of**

pressure

flow

velocity

dsscharge

viscosity.

**ANSWER : : velocity**

**59.Uniform flow occurs when**

the direction and magnitude of the velocity at all points are identical

the velocity of successive fluid pai-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 plsr.e

velocity, depth, pressure, etc. change from point to point in the fluid flow.

**ANSWER : : the magnitude and direction of the velocity do not change from point to point in the fluid**

**60.In a forced vortex, the velocity of flow everywhere within the fluid is**

maximum

minimum

zero

non-zero finite

unpredictable.

**ANSWER : : non-zero finite**

**61.All the terms of energy in Bernoulli’s equation have dimension of**

energy

work

mass

length

time.

**ANSWER : : length**

**62A streamline is defined as the line**

parallel to central axis flow

parallel to outer surface of pipe

of equal yelocity in a flow

along which the pressure drop is uniform

which occurs in all flows.

**ANSWER : : of equal yelocity in a flow**

**63.The region between the separation streamline and the boundary surface of the solid body is known as**

wake

drag

lift

boundary layer

aerofoil section.

**ANSWER : : wake**

**64.The total energy of each particle at various places in the case of perfect incompres sible fluid flowing in continuous sream**

keeps on increasing

keeps on decreasing

remains constant

may increase/decrease

unpredictable.

**ANSWER : : remains constant**

**65.Normal depth in open channel flow is the depth of flow corresponding to**

steady flow

unsteady flow

laminar flow

uniform flow

critical flow.

**ANSWER : : uniform flow**

**66.The pressure in Pascals at a depth of 1 m below the free surface of a body of water will be equal to**

1 Pa

91Pa

9 Pa

90 Pa

9100 Pa.

**ANSWER : : 90 Pa**

**67.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 tc**

10 kg

100 kg

1000 kg

1 kg

10,000 kg.

**ANSWER : : 10 kg**

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

minimum

maximum

zero

negative value

could be any value.

**ANSWER : : could be any value.**

**69.Cavitation will begin when**

the pressure at any location reaches an absolute pressure equal to the saturated vapour pressure of the liquid

pressure becomes more than critical pressure

flow is increased

pressure is increased

none of the above.

**ANSWER : : the pressure at any location reaches an absolute pressure equal to the saturated vapour pressure of the liquid**

**70.Bernoulli equation deals with the law of conservation of**

mass

momentum

energy

work

force.

**ANSWER : : energy**

**71Principle of similitude forms the basis of**

comparing two identical equipments

designing models so that the result can be converted to prototypes

comparing similarity between design and actual equipment

hydraulic designs

performing acceptance tests.

**ANSWER : : designing models so that the result can be converted to prototypes**

**72.Two pipe systems can be said to be equivalent, when the following quantites are same**

friction loss and flow

length and diameter

flow and length

friction factor and diameter

velocity and diameter.

**ANSWER : : friction loss and flow**

**73.For pipes, turbulent flow occurs when Reynolds number is**

less than 2000

between 2000 and 4000

more than 4000

less than 4000

none of the above.

**ANSWER : : more than 4000**