BPSC Exam 2025: Integrated 70th Combined Main (Written) Competitive Examination, Optional, Mechanical Engineering
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Serial No.
Booklet Series
02/GO/CC/M-2025 – 20
I
Candidate’s Roll Number
Question Booklet
I
MECHANICAL ENGINEERING
Time Allowed : 2 Hours Maximum Marks : 100
Read the following instructions carefully before you begin to answer the questions.
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1. 5.
plate of length L, the average convection the momentum correction factor is
(A) 3/2
K L (B) 1.0
(A) hx dx
L 0
(C) 2.0
1 L
(B) hx dx
K 0 (D) 4/3
1 L
(C) hx dx
L 0
6. A ball moving with a momentum of
L L
(D) hx dx 15 kg.m/s strikes a wall at an angle of
K 0
The impulse imparted to the ball is
2. In a split air conditioner, the compressor
(A) Zero
is typically located
(B) 15 2 kg.m/s
(A) In the ceiling unit
(C) 10 3 kg.m/s
(B) Inside the indoor unit
(D) 15 3 kg.m/s
(C) Inside the wall
(D) In the outdoor unit
7. The modulus of resilience is the ratio of
(A) Strain energy per unit stress to the
3. Operating Characteristic (OC) curve
shows the probability of acceptance volume
verses fraction of (B) Maximum strain energy to yield
(A) All items strength
(B) Defective items (C) Proof resilience to the material’s
(C) Rejected items Young’s modulus
(D) Acceptable items (D) Proof resilience to the volume of the
material
4. If 1200 K and 300 K are the maximum
and minimum temperatures in an Otto
cycle, then for the ideal conditions the 8. Fixture used for internal grinding
temperature after compression should be operation is
(A) 900 K (A) Latch
(B) 400 K (B) Mandrel (plane type)
(C) 600 K (C) Chuck
(D) 750 K (D) Mandrel (tapered type)
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9. 13. A slider sliding at 10 cm/s on a link which
is rotating at 60 rpm is subjected to
(A) Air and refrigerant
Coriolis acceleration of magnitude
(B) Liquid and vapor refrigerant
(C) Oil and refrigerant (A) 4 cm/s2
(D) Water and refrigerant (B) 40 2 cm/s2
(C) 0.4 cm/s2
10. The condition that is necessary for
thermodynamic equilibrium is/are (D) 40 cm/s2
(A) All the three equilibriums
(B) Mechanical equilibrium
14.
(C) Chemical equilibrium
(D) Thermal equilibrium (A) Maximum exergy intake to minimum
exergy intake
11. The electrode materials in Plasma Arc (B) Actual exergy intake to minimum
Machining are
exergy intake
(A) Nickel and silver
(C) Minimum exergy intake to actual
(B) Steel and brass
exergy intake
(C) Tungsten and copper
(D) Titanium and graphite (D) Actual exergy intake to maximum
exergy intake
12. A steel specimen is subjected to the
following principal stresses: 95 MPa
tensile, 60 Mpa tensile and 30 Mpa 15.
compressive. If the yield strength for the
steel specimen is 250 Mpa; the factor
of safety as per maximum shear stress
(A) Inertia force to gravity force
theory will be
(A) 2.0 (B) Inertia force to pressure force
(B) 1.25 (C) Pressure force to viscous force
(C) 1.5
(D) Viscous force to gravity force
(D) 1.75
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16. The air compressor capacity is often 19. In a uniformly heated long circular tube
(A) Compressed air at delivery pressure
diameter is reduced by half, the heat
(B) Free air
(C) Standard air (A) Increase by a factor of four
(B) Be double the original value
(D) Compressed air
(C) Be half the original value
(D) Remain the same as before
17.
of evaporation of the liquid ammonia
20. The basic form of Bernoulli’s equation
passing through the evaporator in a does not include the
domestic Electrolux refrigeration
(A) Potential head
system is
(B) Pressure head
(A) Hydrogen (C) Manometric head
(D) Velocity head
(B) Water
(C) Ammonia
21. Drilling jigs
(D) Mercury
(A) Can not be used for reaming
18. If a certain mass of moist air in an (B) Can be open type only
air tight vessel is heated to a higher
(C) Can be closed type only
temperature, then
(D) Can be both open and closed type
(A) Relative humidity of the air
decreases
(B) S 22. The tally sheet data from a work
increases sampling study provides information on
(C) S (A) Work environment quality
decreases (B) Wasted motions
(D) Relative humidity of the air
increases (D) Time spent on various tasks
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23. The pump most commonly used for 26. In a reverted gear train with four gears,
two gears A (18 teeth) and B (54 teeth)
are meshing, B – C is a compound gear,
(A) Piston pump
while C (24 teeth) and D are meshing.
(B) Centrifugal pump If all the gears have equal module and
(C) Diaphragm pump gear D rotates at 90 rpm, the speed of
gear A is
(D) Screw pump
(A) 1800 rpm
(B) 15 rpm
24. The key feature of Benson boiler that (C) 150 rpm
distinguishes it from other high-pressure (D) 180 rpm
boilers is
27. The index that correlates the combined
(A) It uses natural circulation of water effects of air temperature, relative
humidity and air velocity on the human
(B) Its total weight is 20% more body is known as
(A) Comfort index
(C) It operates at subcritical pressures (B) Mean radiant temperature
(C) Effective temperature
(D) It operates without a steam drum
(D) Dew point temperature
25. Which of the following is not an
28. The lowest thermal diffusivity is of
advantage of the steam-jet refrigeration
(A) Rubber
system ?
(B) Iron
(A) Utilizes low-grade energy in the (C) Lead
boiler
(D) Aluminium
(B) Can be used in remote areas without
electricity 29. The most suitable belt for cross belt drive
is/are
(C) Has a high COP due to efficient
(A) Running belt
energy use
(B) Flat belt
(D) Has simple construction with minimal
(C) V-belt
moving parts (D) All of the above
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30. The main purpose of the MPFI system in 34. The ratio of the amplitude of the steady-
a gasoline engine is to state response of forced vibrations to the
(A) Control the ignition timing for fuel
combustion
known as
(B) I
engine
(C) Supply the correct air-fuel ratio to each (B) Damping ratio
cylinder
(C) Damping factor
(D) Enhance the engine’s exhaust system
performance (D) Transmissibility
31. In a vapour compression refrigeration 35. Unit Load method is also known as
system, an oil separator is installed
between (A) Virtual Work Load Method
(A) Throttle valve and evaporator
(B) Euler’s Method
(B) Evaporator and condenser
(C) Compressor and condenser (C) Castigliano’s Method
(D) Condenser and throttle valve
(D) Real Work Method
32. The thickness of turbulent boundary
layer at a distance (x) from the leading 36. The commonly used material for
manufacturing of photovoltaic cells is
(A) x4/5
(A) Aluminium
(B) x1/5
(B) Copper
(C) x2/5
(D) x3/5 (C) Silicon
(D) Iron
33. An assembly line has 21 tasks divided
into 5 workstations. The total task time 37.
is 85 minutes, and the cycle time is 20 known as
(A) Von Kármán effect
(A) 100%
(B) Nucleate effect
(B) 4.2%
(C) Boiling regimes
(C) 17%
(D) Leiden frost effect
(D) 85%
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38. For a heat engine operating on the 41. 18 : 8 stainless steel
Carnot cycle, the work output is 1/4th of
(A) Is not machinable
the heat transferred to the cold system.
(B) Has excellent machinability
(A) 80% (C) Has good machinability
(B) 20%
(D) Has fair machinability
(C) 25%
(D) 75%
42. In a service centre, cars arrive according
to a Poisson distribution with a mean of
39. In Ultrasonic Machining, the 2 cars per hour. The time for servicing
magnetostrictor converts magnetic a car is exponentially distributed with
energy into a mean of 15 minutes. The expected
(A) Chemical energy waiting time in the queue is
(B) Mechanical energy (A) 30 minutes
(C) Electrical energy (B) 10 minutes
(D) Thermal energy
(C) 15 minutes
(D) 25 minutes
40. The temperature distribution
T T
e mx is valid for
T0 T 43. If a shaft is simultaneously subjected to
a torque T and a bending moment M,
(A) F
the ratio of maximum bending stress and
temperature at end
maximum shearing stress is
(B) I (A) T/M
(C) F
(B) 2M/T
end
(D) F (C) M/T
convection at end
(D) 2T/M
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44. In a slider-crank mechanism, the velocity 47. The rotor of a ship rotates in a clockwise
of the piston becomes maximum when direction when viewed from the stern, and
the ship takes a left turn. The effect of the
(A) Crank is 120 with the line of stroke
gyroscopic couple acting on it will be
(B) Crank and connecting rod are in line (A) To raise the stern and lower the
with each other bow
(C) Crank and connecting rod are mutually (B) To raise the bow and stern
perpendicular (C) To lower the bow and stern
(D) Crank is perpendicular to the line of (D) To raise the bow and lower the
stern
stroke of the piston
45. For steady-state heat transfer with 48. In D’Alembert’s principle, the term ‘ma’
a constant thermal conductivity, the represents
(A) The centripetal force acting on the
heat conduction through a cylinder is body
(B) The force due to gravity
(A) Exponential
(C) The net applied force on the body
(B) Linear
(D) The inertial force opposing
(C) Logarithmic acceleration
(D) Parabolic
49. Which of the following statement is
incorrect about ABC analysis ?
46. The operation of Johansson Mikrokator (A) It assumes that all items need the
same level of control
rely on the
(B) Inventory may be categorized by
(A) Optical interference
factors other than monetary value
(B) Changes in Electrical resistance
three groups based on annual
(C) Changes in air pressure
monetary value
(D) Twisting of a thin metal strip (D) It applies the Pareto principle
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50. Two masses of 6.2 kg and 13.4 kg are 54. An automatic clutch which is controlled
fastened to ends of a cord passing over by engine speed is
a frictionless pulley. The acceleration of
the resulting motion is (A) Disc clutch
(A) 19.6 m/s2 (B) Centrifugal clutch
(B) 3.6 m/s2
(C) Cone clutch
(C) 7.2 m/s2
(D) 9.8 m/s2 (D) Fluid clutch
55. For applying Lami’s theorem, necessary
51. When vibrations are initiated by an initial condition is
energy present in the system, and no
external force acts thereafter, these (A) Forces must be perpendicular and
vibrations are called in equilibrium
(A) Transient vibrations
(B) Forces must be non-coplanar and
(B) Free vibrations
concurrent
(C) Forced vibrations
(C) Forces must be parallel and
(D) Random vibrations
non-concurrent
(D) Forces must be concurrent and
52. The most commonly used tool to measure coplanar
temperature in the cutting zone during
the machining process is 56. Pressure vessels are not made in a
(A) Radiation pyrometer rectangular shape because
(B) Embedded thermocouple (A) Cylindrical shapes are transport-
(C) Temperature sensitive paint friendly
(D) Tool-work thermocouple
(C) Cylindrical vessels are practiced
53. The motion of a particle is given by the
(D) Stress concentration at corners
equation s = 2t3 + 3t (where s is distance
in meters and t is time in seconds).
Starting from t = 0, to attain a velocity 57. Holes in Nylon buttons are made by
of 9 m/s, the particle will have to travel a
distance of (A) Laser Beam Machining (LBM)
(A) 20 m (B) Electro Discharge Machining (EDM)
(B) 5 m
(C) Chemical Machining (CHM)
(C) 10 m
(D) 15 m (D) Ultrasonic Machining (USM)
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58. According to Euler’s theory, for a column 62. The nuclear reactor designed to produce
with both ends pinned (hinged), if the
length of the column is doubled and all
other factors remain constant, the critical
(A) Heavy Water Reactor (HWR)
buckling load will
(A) Remains unchanged (B) Pressurized Water Reactor (PWR)
(B) Increases by a factor of two
(C) Boiling Water Reactor (BWR)
(C) Decreases by a factor of four
(D) Decreases by a factor of sixteen (D) Fast Breeder Reactor (FBR)
59. To avoid degeneracy, the minimum 63. In the velocity reduction method for
number of occupied cells required in a designing air conditioner ducts, the
transportation matrix with 8 rows and
velocities in the ducts are adjusted to
7 columns are
(A) 42 (A) E
(B) 14 (B) Reduce noise
(C) 15
(C) Maintain equal pressure drop
(D) 41
(D) Balance pressure at the outlets
60.
continuity equation is
64. A light foot bridge is to be provided over
(A) u = kx2y2, v = ky2
(B) u = kx, v = ky a river crossing of 80 m span. If the
(C) u = – kx, v = ky central dip is 6 m, the length of each
(D) u k x, v k y
cable is
61. For a radiation shield, the parameter that (A) 90.0 meters
should be highest is
(B) 81.2 meters
(A) Emissivity
(B) Absorptivity (C) 84.6 meters
(C) R
(D) 88.5 meters
(D) Transmissivity
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65. For low and moderate-speed engines, 69.
the cam follower should move with thermodynamics is expressed as
(A) Cycloidal motion (A) Q= W
(B) Uniform velocity
(B) W= U
(C) Uniform acceleration
(C) W=– U
(D) Harmonic motion
(D) Q= U
66. The state of stress at a point under plane 70. The following is an example of a
stress condition is x = 30 MPa, thixotropic substance
(A) Printer ink
y = 18 MPa and xy = 8 MPa. The
radius of Mohr’s circle representing the (B) Quick sand
given state of stress is (C) Gypsum
(D) Water
(A) 24 Mpa
(B) 10 MPa
71. For a plane wall of thickness L with
(C) 12 MPa
uniform internal heat generation qg per
(D) 22 Mpa
unit volume, the temperature difference
between the mid-plane and the surface is
67. If a material is restrained from expanding
while heated, the resulting stress is (A) qgL2/16k
(A) Compressive stress (B) qgL2/2k
(B) Hoop stress
(C) qgL2/4k
(C) Shear stress
(D) qgL2/8k
(D) Tensile stress
72. Knock in a diesel engine occurs due to
68. The type of jig used for drilling holes in a
circular pattern is (A) Shortening of the delay period
(A) Indexing jig (B) Delayed combustion of the initial
portion of the charge
(B) Plate jig
(C) Instantaneous combustion of the
(C) Box jig
(D) Template jig (D) Instantaneous auto-ignition of the
last part of the charge
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73. The primary reason for the outer surface 77. In the basic EOQ model, if the ordering
of the aircraft getting heated during
cost doubles and all other factors remain
(A) Energy dissipation from aircraft the same, the EOQ will
systems
(A) Remains unchanged
(B) Solar radiation
(C) Frictional heating due to airspeed (B) Increase by 21%
(D) Metabolic heat from passengers
(C) Increase by 41%
74. A 5 m long ladder is resting on a smooth (D) Increase by 71%
vertical wall with its lower end 3 m from
of friction between the ladder and the 78. Enthalpy (h) is expressed as
(A) h = u (1 – pv)
(A) 3/8
(B) 1/2 (B) h = u + pv
(C) 1/3 (C) h = u – pv
(D) 3/5 (D) h = u (1 + pv)
75. The materials for which Poisson’s ratio is 79. A body weighs 1 kg in air, 0.8 kg in water
close to zero is
oil is
(A) Lead (A) 2.5
(B) Cork (B) 1
(C) Aluminium (C) 1.5
(D) Rubber (D) 2
76. In Electro Discharge Machining (EDM)
80. The Curtis turbine is a steam turbine with
process, the gap between the tool and
workpiece should be (A) Single-stage expansion
(A) 0.0025 mm to 0.005 mm
(B) Reaction stages
(B) 2.5 mm to 5 mm
(C) Impulse blades
(C) 0.25 mm to 0.5 mm
(D) 0.025 mm to 0.05 mm (D) Aerofoil blades
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81. 85. In a maximization problem, the shadow
an azeotropic mixture price (or dual value) represents
(A) R-507A
(A) The cost reduction with a decrease in
(B) R-12
resource usage
(C) R-134a
(D) R-407C
additional unit of a constrained
82. In a simply supported beam, for the resource
same total load and span, the ratio of the
Load (UDL) to that under a same point one unit of a resource
load is
(D) The price to pay for acquiring more
(A) 7/8
resources
(B) 3/8
(C) 1/2
(D) 5/8 86. Entropy is a
(A) Point function, extensive property
83. Tool wear caused by abrasion from hard
particles and inclusions in the workpiece is (B) Path function, intensive property
(A) Chipping
(B) Crater wear (C) Path function, extensive property
(C) Flank wear
(D) Point function, intensive property
(D) Nose wear
87. At a Mach number of 0.5, the
84. ‘Lay’ in surface texture refers to the
concentration of pressure pulses
(A) Distance between the wavy surface created by an object is
features
(A) Uniform outside the Mach cone
(B) Direction of the predominant surface
pattern (B) Larger ahead of the object
(C) Height of the surface irregularities (C) Larger behind the object
(D) Spacing between successive peaks (D) Uniform within the Mach cone
or valleys
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88. In a heat exchanger the hot gas enters 92. Jars of pickles are sampled and weighed,
at 200°C and leaves at 160°C while the
and the sample measurements are plotted
cold air enters at 50°C and leaves at
150°C. The capacity ratio is on control charts. The target weight for
(A) 0.4 each jar should be exactly 250 grams. The
(B) 2.5 appropriate control chart is
(C) 2.0
(A) both x-bar and R-charts
(D) 0.5
(B) p-charts
89. (C) c-charts
is the speed of a geometrically similar
(D) both p- and c-charts
turbine which would produce
(A) Unit power under unit speed
93. A diesel engine has a compression ratio
(B) Unit discharge under unit head
of 16 and cut-off takes place at 8% of the
(C) Unit discharge under unit speed stroke. The cut-off ratio is
(D) Unit power under unit head
(A) 2.2
(B) 1.6
90. The maximum value of the secondary
unbalanced force as compared to (C) 1.8
the maximum value of the primary
unbalanced force in reciprocating (D) 2.0
engines is
(A) n2 times
94. The law governing the distribution of
(B) 1/n times
(C) n times radiant energy over wavelength for a
(D) 2n times
referred as
91. In explosive forming, the stand-off
(A) Lambert’s law
distance is the distance between
(A) Workpiece and mold (B) Planck’s law
(B) Explosive and mold
(C) Wien’s formula
(C) Explosive and workpiece
(D) Explosive and shock waves (D) Kirchhoff’s law
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95. The function of a regenerator in a gas
98. LASER is produced by
turbine is
(A) Graphite
(A) T
(B) Aluminium
chamber
(C) Ruby
(B) To heat the air between different
(D) Diamond
stages of compression
(C) To heat the air between different
99. A fully insulated and completely empty
stages of expansion
(D) To heat compressed air entering
combustion chamber
96. The circumferential stress in a hollow
circular rotating disc is maximum at
(A) The geometric mean radius
(B) The inner radius
(C) The outer radius
in the charged tank
(D) The mean radius
(D) None of the above
97. The instantaneous centre of rotation of
100.
the piston in a slider-crank mechanism diameter of the stream is the least and
lies at
(A) Throat
stroke
(B) Vena contracta
(B) The crankpin centre
(C) Flow nozzle
(C) The piston pin centre
(D) The crankshaft bearing centre
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Source: Bihar Public Service Commission. Question paper published by Bihar Public Service Commission.