# Fluid Mechanics and Machinery

## ME4I

### 22445

#### Multiple Choice Questions (MCQs)

1   The specific gravity of a fluid has
(A)   The same unit as that of mass density
(B)   The same unit as that of weight density
(C)   The same unit as that of specific volume
(D)   No unit

2   The specific volume of a fluid is the reciprocal of
(A)   weight density
(B)   mass density
(C)   specific weight
(D)   specific volume

3   One liter of a certain fluid weighs 8N. What is its specific volume?
(A)   2.03 x 10– 3 m3/kg
(B)   20.3 x 10– 3 m3/kg
(C)   12.3 x 10– 3 m3/kg
(D)   1.23 x 10– 3 m3/kg

4   What is the correct formula for absolute pressure?
(A)   Pabs = Patm – Pgauge
(B)   Pabs = Pvacuum – Patm
(C)   Pabs = Pvacuum + Patm
(D)   Pabs = Patm+ Pgauge

5   The fluid will rise in capillary when the capillary is placed in fluid, if
(A)   The adhesion force between molecules of fluid and tube is less than the cohesion between liquid molecules
(B)   the adhesion force between molecules of fluid and tube is more than the cohesion between liquid molecules
(C)   the adhesion force between molecules of fluid and tube is equal to the cohesion between liquid molecules
(D)   None of these

6   The intensity of pressure at any point, in a liquid, is
(A)   Directly proportional to the area of the vessel containing liquid
(B)   Directly proportional to the depth of liquid from the surface
(C)   Directly proportional to the length of the vessel containing liquid
(D)   Inversely proportional to the depth of liquid from the surface

7   A manometer is used to measure
(A)   Atmospheric pressure
(B)   Pressure in pipes and channels
(C)   Pressure in Venturi meter
(D)   Difference of pressures between two points in a pipe

8   For pipes, laminar flow occurs when Reynolds number is
(A)   Less than 2000
(B)   Between 2000 and 4000
(C)   More than 4000
(D)   Less than 4000

9   Property of a fluid by which molecules of different kinds of fluids are attracted to each other is called
(B)   Cohesion
(C)   Viscosity
(D)   Compressibility

10   Venturi meter is used to
(A)   Measure the velocity of a flowing liquid
(B)   Measure the pressure of a flowing liquid
(C)   Measure the discharge of liquid flowing in a pipe
(D)   Measure the pressure difference of liquid flowing between two points in a pipe line

11   Capillary action is due to the
(A)   Surface tension
(B)   Cohesion of the liquid
(C)   Adhesion of the liquid molecules and the molecules on the surface of a solid
(D)   All of the above

12   According to Bernoulli’s equation for steady ideal fluid flow
(A)   Principle of conservation of mass holds
(B)   Velocity and pressure are inversely proportional
(C)   Total energy is constant throughout
(D)   The energy is constant along a streamline but may vary across streamlines

13   Differential manometer is used to measure
(A)   Pressure in pipes, channels etc.
(B)   Atmospheric pressure
(C)   Very low pressure
(D)   Difference of pressure between two points

14   According to Bernoulli’s equation
(A)   Z + p/w + v2/2g = constant
(B)   Z + p/w – v2/2g = constant
(C)   Z – p/w + v2/2g = constant
(D)   Z – p/w – v2/2g = constant

15   Newton’s law of viscosity is a relationship between
(A)   Pressure, velocity and temperature
(B)   Shear stress and rate of shear strain
(C)   Shear stress and velocity
(D)   Rate of shear strain and temperature

16   The unit of dynamic viscosity in S.I. units is
(A)   N-m/s2
(B)   N-s/m2
(C)   Poise
(D)   Stoke

17   One liter of water occupies a volume of
(A)   100 cm3
(B)   250 cm3
(C)   500 cm3
(D)   1000 cm3

18   The continuity equation is connected with
(A)   Open channel/pipe flow
(B)   Compressibility of fluids
(C)   Conservation of mass

19   A Piezometer tube is used only for measuring
(A)   Low pressure
(B)   High pressure
(C)   Moderate pressure
(D)   Vacuum pressure

20   A pitot tube is used to measure the
(A)   Velocity of flow at the required point in a pipe
(B)   Pressure difference between two points in a pipe
(C)   Total pressure of liquid flowing in a pipe
(D)   Discharge through a pipe

21   Surface tension has the units of
(A)   Newton-sec/m
(B)   Newton-m/sec
(C)   Newton/m
(D)   Newton

22   The center of pressure of a surface subjected to fluid pressure is the point
(A)   On the surface at which resultant pressure acts
(B)   On the surface at which gravitational force acts
(C)   At which all hydraulic forces meet
(D)   Similar to metacenter

23   Cavitation is caused by
(A)   High velocity
(B)   High pressure
(C)   Weak material
(D)   Low pressure

24   An ideal flow of any fluid must fulfill the following
(A)   Newton’s law of motion
(B)   Newton’s law of viscosity
(C)   Pascal’ law
(D)   Continuity equation

25   The kinematic viscosity is the
(A)   Ratio of absolute viscosity to the density of the liquid
(B)   Ratio of density of the liquid to the absolute viscosity
(C)   Product of absolute viscosity and density of the liquid
(D)   Product of absolute viscosity and mass of the liquid

26   Which of the following instruments is used to measure flow on the application of Bernoulli’s theorem?
(A)   Venturi meter
(B)   Orifice plate
(C)   Nozzle
(D)   All of the above

27   The height of a water column equivalent to a pressure of 0.15 MPa is
(A)   15.3 m
(B)   25.3 m
(C)   35.3 m
(D)   45.3 m

28   The velocity of the liquid flowing through the divergent portion of a Venturi meter
(A)   Remains constant
(B)   Increases
(C)   Decreases
(D)   Depends upon mass of liquid

29   Which one of the following is a major loss?
(A)   Frictional loss
(B)   Shock loss
(C)   Entry loss
(D)   Exit loss

30   On which of the factors does the co-efficient of bend in a pipe depend?
(A)   Angle of bend and radius of curvature of the bend
(B)   Angle of bend and radius of the pipe
(C)   Radius of curvature of the bend and pipe and angle of bend
(D)   Radius of curvature of the bend and pipe

31   Energy gradient line takes into consideration
(A)   Potential and kinetic heads only
(B)   potential, kinetic and pressure heads
(C)   potential and pressure heads only
(D)   kinetic and pressure heads only

32   The hammer blow in pipes occurs when
(A)   There is excessive leakage in the pipe
(B)   The pipe bursts under high pressure of the fluid
(C)   The flow of fluid through the pipe is suddenly brought to rest by the closing of the valve
(D)   The flow of fluid through the pipe is gradually brought to rest by the closing of the valve

33   What is the ratio of maximum velocity to average velocity, when the fluid is passing through two parallel plates and flow is laminar?
(A)   3/2
(B)   2/3
(C)   4/3
(D)   3/4

34   What is the Darcy-Weisbach formula for heat loss due to friction? Where, f = Darcy’s coefficient of friction
(A)   hf = (f l V2) / (g d)
(B)   hf = (4 f l V2) / (2 g d)
(C)   hf = (f l V2) / (2 g d)
(D)   hf = (16 f l V2) / (2 g d)

35   What is the correct formula for loss at the exit of a pipe?
(A)   hf = (V2 / 2g)
(B)   hf = (2 V2 / g)
(C)   hf = 0.5 (V2 / 2g)
(D)   hL = (4 V2 / g)

36   Which property of the fluid accounts for the major losses in pipes?
(A)   density
(B)   specific gravity
(C)   viscosity
(D)   compressibility

37   The total head loss for the system is equal to_________
(A)   Pipe length
(B)   Pipe diameter
(C)   Width of the reservoir
(D)   Height difference of reservoirs

38   The force analysis on a curved vane is understood using______
(A)   Velocity triangles
(B)   Angle of the plate
(C)   Vane angles
(D)   Plate dimensions

39   The relative velocity is obtained by the equation_________
(A)   u – V1
(B)   V1
(C)   u*V1
(D)   u/V1

40   The flow in a pipe is laminar if the Reynolds number is
(A)   Less than 2000
(B)   Between 2000 and 4000
(C)   Between 4000 and 6000
(D)   Equal to 6300

(A)   Is always below the total energy line
(B)   Is always parallel to the bottom
(C)   Is same as central line of section
(D)   Is always above the total energy line

42   Cavitation is caused by
(A)   High velocity
(B)   Low barometric pressure
(C)   High pressure
(D)   Low pressure

43   A Francis turbine is
(A)   Inward flow reaction turbine
(B)   Inward flow impulse turbine
(C)   Outward flow reaction turbine
(D)   Outward flow impulse turbine

44   Runway speed of a Pelton wheel is
(A)   Actual operating speed
(D)   No load speed when governor mechanism fails

45   In a reaction turbine
(A)   It is possible to regulate the flow without loss
(B)   It must be placed at the foot of the fall and above the tail race
(C)   Work done is purely by the change in the kinetic energy of the jet
(D)   Only part of the head is converted into velocity before the water enters the wheel

46   In a turbine installation gross head is defined as
(A)   The difference of level between the head race and the tail race
(B)   The difference of level between reservoir and downstream
(C)   The difference of head between axis of turbine to discharge stream level
(D)   The head actually used in developing power

47   In reaction turbine the draft tube is used
(A)   To transport water to downstream without eddies
(B)   To reconvert kinetic energy to flow energy by a gradual expansion of the flow cross-section
(C)   To increase the effective head
(D)   To prevent air from entering

48   The magnitude of water hammer depends on
(A)   The length of pipeline
(B)   The speed at which the valve is closed
(C)   To elastic properties of the liquid flowing through the pipe
(D)   All of the above

49   In an impulse turbine
(A)   Water must be admitted over the whole circumference
(B)   It is not possible to regulate the flow without loss
(C)   Wheel must run full and kept entirely submerged in water below the tailrace
(D)   The pressure in the driving fluid as it moves over the vanes is atmospheric

50   Specific speed of reaction turbine is between?
(A)   5 and 50
(B)   10 and 100
(C)   100 and 150
(D)   150 and 300

51   The specific speed of a turbine is given by the equation
(A)   N√P / H3/2
(B)   N√P / H²
(C)   N√P / H5/4
(D)   N√P / H3

52   The overall efficiency of a reaction turbine is the ratio of
(A)   Power produced by the turbine to the energy actually supplied by the turbine
(B)   Actual work available at the turbine to the energy imparted to the wheel
(C)   Work-done on the wheel to the energy (or head of water) actually supplied to the turbine
(D)   None of the above

53   The force exerted by a jet of water (in a direction normal to flow) impinging on a fixed plate inclined at an angle θ with the jet is
(A)   (waV/2g) × sin θ
(B)   (waV/g) × sin θ
(C)   (waV²/2g) × sin 2θ
(D)   (waV²/g) × sin θ

54   The specific speed of a hydraulic turbine depends upon
(A)   Speed and power developed
(B)   Discharge and power developed
(C)   Speed and head of water
(D)   Speed, power developed and head of water

55   The cavitation in reaction turbines is avoided, to a great extent by
(A)   Installing the turbine below the tail race level
(B)   Using stainless steel runner of the turbine
(C)   Providing highly polished blades to the runner
(D)   All of the above

56   In a Kaplan turbine runner, the numbers of blades are generally between
(A)   2 to 4
(B)   4 to 8
(C)   8 to 16
(D)   16 to 24