← MES Jr. Grade
Past Questions
A cotter joint is used to connect two rods which are in
A)
tension only
B)
compression only
C)
tension and compression
D)
shear only
A cotter joint is used to connect two co-axial rods that transmit axial force. It can be used when the rods are subjected to either tension or compression. Hence, the correct answer is 'tension and compression'. Option (a) is incomplete because cotter joints are not limited to tension only, and (b) and (d) are incorrect because cotter joints are not meant for shear-only loading.
The efficiency of a welded joint, compared to a riveted joint is
A)
more
B)
less
C)
equal
D)
unpredictable
A welded joint is generally more efficient than a riveted joint because welding provides a continuous connection without holes for rivets. Riveted joints weaken the plate due to perforations and stress concentration, while welded joints can transmit load more uniformly. Hence, the efficiency of a welded joint is more than that of a riveted joint.
The maximum bending moment in a simply supported beam carrying a total load W, uniformly distributed on the entire span L is equal to
A)
WL/2
B)
WL/3
C)
WL/4
D)
WL/8
For a simply supported beam with a uniformly distributed load W over the full span L, the reactions at the supports are W/2 each. The bending moment is maximum at midspan. The maximum bending moment is given by Mmax = wL^2/8, where w = W/L. Substituting gives Mmax = (W/L) × L^2 / 8 = WL/8. Hence, the correct answer is (d). The other options do not match the standard bending moment formula for a full-span UDL.
A round key is used for
A)
light duty
B)
medium duty
C)
heavy duty
D)
extra heavy duty
A round key is generally used for medium duty applications. It is suitable where moderate torque transmission is required. Light duty keys are usually saddle keys, while heavy and extra heavy duty applications typically use sunk keys or special keys designed for greater load transmission.
The product of circular pitch and diameteral pitch is equal to
A)
module
B)
unity
C)
D)
1/
For gears, circular pitch (pc) = πm and diametral pitch (Pd) = 1/m, where m is the module. Therefore, pc × Pd = (πm) × (1/m) = π. Hence the correct answer is π. Option (a) module is incorrect because module is the reciprocal of diametral pitch, not the product. Option (b) unity is incorrect because the product is not 1. Option (d) 1/π is the reciprocal of the correct value.
A beam is loaded as cantilever. If the load at the free end is increased, the failure will occur
A)
at the point of the load
B)
at the middle of the beam
C)
at the fixed end of the beam
D)
at any location of the beam
In a cantilever beam with a load at the free end, the bending moment is maximum at the fixed support and zero at the free end. Since failure in bending occurs where the bending stress is highest, the beam will fail at the fixed end. The other options are incorrect because the load point has no maximum moment, the middle is not the critical section, and failure does not occur at any arbitrary location.
Rankine’s theory of failure is applicable for which of the following type of materials?
A)
brittle
B)
ductile
C)
elastic
D)
plastic
Rankine’s theory is the maximum principal stress theory. It states that failure occurs when the maximum principal stress reaches the ultimate stress in simple tension. This theory is mainly applicable to brittle materials such as cast iron, glass, and concrete, which fail suddenly with little plastic deformation. Ductile materials are better explained by theories like Tresca and von Mises.
The hydraulic unit used to minimize frictional loss in pipe line is called as
A)
safety tank
B)
surge tank
C)
relief tank
D)
pressure tank
A surge tank is a hydraulic unit provided in a pipeline to absorb sudden pressure changes and reduce water hammer effects. By smoothing out flow fluctuations, it helps minimize frictional and pressure losses in the pipe line. A safety tank, relief tank, and pressure tank are not the standard term used for this purpose in hydraulic machinery.
The boundary layer exists in which of the following?
A)
Flow of real fluids
B)
Flow of ideal fluids
C)
Flow over flat surfaces only
D)
Pipe-flow only
A boundary layer forms when a real fluid flows over a surface because viscosity causes the fluid velocity to change from zero at the wall to the free-stream value away from it. Ideal fluids are inviscid, so they do not form a boundary layer. It is not limited to flat surfaces or pipe flow; it can occur over any solid boundary.
In a steady flow in a varying section pipe if the diameter is doubled the kinetic energy will
A)
be doubled
B)
increase 4 times
C)
increase 8 times
D)
decrease to one sixteenth
For steady incompressible flow, discharge Q = A v is constant. If the pipe diameter is doubled, the cross-sectional area becomes 4 times, so velocity becomes 1/4. Kinetic energy per unit mass is proportional to v^2, hence it becomes (1/4)^2 = 1/16 of the original. Therefore, the kinetic energy decreases to one sixteenth.
In case of S.I. engine, to have best thermal efficiency the fuel-air mixture ratio should be
A)
rich
B)
lean
C)
may be rich or lean
D)
same
In a spark-ignition (S.I.) engine, best thermal efficiency is generally obtained with a slightly lean fuel-air mixture. A lean mixture contains excess air, which promotes more complete combustion and reduces fuel wastage, improving efficiency. A rich mixture is used when more power is needed, but it lowers thermal efficiency because of incomplete combustion and higher fuel consumption. Therefore, the correct answer is lean.
A fluid in which resistance of deformation is independent of the shear stress is known as
A)
Bingham plastic fluid
B)
Pseudo plastic fluid
C)
Dilatent fluid
D)
Newtonian fluid
A Newtonian fluid has a linear relationship between shear stress and rate of shear strain, so its viscosity remains constant and the resistance to deformation is independent of the applied shear stress. In contrast, Bingham plastic fluids require a yield stress, pseudo-plastic fluids are shear-thinning, and dilatant fluids are shear-thickening.
In parallel flow heat exchangers, the two fluids i.e. hot and cold travel in the
A)
same direction
B)
opposite direction
C)
cross direction
D)
axial direction
In a parallel flow heat exchanger, the hot and cold fluids enter from the same end and move in the same direction. Hence, the correct answer is (a) same direction. Option (b) describes counter-flow, and (c) describes cross-flow. Option (d) is not a standard classification of heat exchanger flow arrangement.
Specific speed of turbine is indicated as
A)
N Q / H3/4
B)
N P / H5/4
C)
N Q / H2/3
D)
N P / H3/4
Specific speed of a turbine is defined as the speed of a geometrically similar turbine that would develop unit power under unit head. Its standard expression is Ns = N\u221aP / H^(5/4). Among the given options, this matches option (b). Options (a), (c), and (d) use incorrect powers of H or Q.
One tonne of refrigeration is approximately equal to
A)
14,000 kJ/hr
B)
3.8 kW
C)
230 kJ/min
D)
all of these
1 tonne of refrigeration (1 TR) is the rate of heat removal required to freeze 1 tonne of water at 0°C into ice at 0°C in 24 hours. Its standard value is about 3.517 kW, which is approximately 211 kJ/min or 12,660 kJ/hr. In many exam contexts, rounded/approximate values are used, and the given options are intended to represent the same order of magnitude. Since 3.8 kW is a rough approximation of 1 TR, and 230 kJ/min and 14,000 kJ/hr are also approximate conversions, the intended answer is 'all of these'.
An isentropic process is always
A)
irreversible and adiabatic
B)
reversible and isothermal
C)
reversible and adiabatic
D)
frictionless and irreversible
An isentropic process is one in which entropy remains constant. For a process to be isentropic, it must be both adiabatic (no heat transfer) and reversible (no entropy generation). Hence, the correct answer is reversible and adiabatic. The other options are incorrect because irreversible processes generate entropy, and isothermal means constant temperature, not constant entropy.
An impulse turbine
A)
operates submerged
B)
requires draft tube
C)
is most suited for low head applications
D)
operates by initial complete conversion to kinetic energy
An impulse turbine works by first converting the entire available head into kinetic energy in a nozzle. The high-velocity jet then strikes the runner buckets and produces work. It does not operate submerged, does not require a draft tube, and is generally suited for high head, low discharge applications rather than low head.
The thermal property that remains same on the two sides of the impulse wheel of a steam turbine is
A)
heat
B)
temperature
C)
velocity
D)
pressure
In an impulse turbine, the entire pressure drop of steam occurs in the nozzle, not in the moving blades (impulse wheel). Therefore, across the two sides of the impulse wheel, the pressure remains essentially the same. The steam’s velocity changes as it passes over the blades, but pressure does not. Hence, the correct answer is pressure.
A venturimeter is used for measuring
A)
pressure
B)
flow rate
C)
total energy
D)
piezometric head
A venturimeter is a differential pressure device used to measure the discharge or flow rate of a fluid flowing through a pipe. It works on Bernoulli’s principle: as fluid passes through the constricted throat, velocity increases and pressure decreases, and this pressure difference is used to calculate flow rate. It does not directly measure pressure, total energy, or piezometric head.
In steam nozzle for the same pressure ratio the dryness fraction of exit steam increases due to considering the effect of
A)
friction loss
B)
contraction loss
C)
velocity loss
D)
pressure loss
In a steam nozzle, if friction is considered, part of the available enthalpy drop is dissipated as internal irreversibility. For the same pressure ratio, the actual expansion is less ideal, so the steam at the exit is less wet than in the ideal case, i.e., the dryness fraction increases. Hence the correct effect is friction loss. Contraction loss and velocity loss are not the standard reason for increase in exit dryness fraction in nozzle theory, and pressure loss is not the specific cause here.
For high head and low discharge, the hydraulic machinery selected is
A)
Francis turbine
B)
Kaplan turbine
C)
Pelton turbine
D)
none of these
For a high head and low discharge condition, an impulse turbine is preferred. The Pelton turbine is specifically designed for high head, low flow rate applications. Francis turbine is used for medium head and medium discharge, while Kaplan turbine is used for low head and high discharge. Therefore, the correct answer is Pelton turbine.
The compression ratio of Diesel engine may have the range of
A)
8 to 10
B)
10 to 15
C)
16 to 20
D)
none of these
A Diesel engine works on compression ignition, so it requires a much higher compression ratio than a petrol engine. Typical Diesel engine compression ratios are in the range of about 16:1 to 20:1. Option (a) 8 to 10 is too low and is more typical of petrol engines. Option (b) 10 to 15 is still generally below the usual Diesel range. Therefore, the correct answer is (c) 16 to 20.
A turbulent flow is considered steady when
A)
the algebraic sum of velocity fluctuations is zero
B)
the velocity at a point does not change with time
C)
temporal mean velocity at a point remains constant with time
D)
the discharge remains constant
In turbulent flow, the instantaneous velocity at a point keeps fluctuating. A flow is called steady only when the time-averaged (temporal mean) velocity at a point does not change with time. Option (b) is incorrect because it refers to instantaneous velocity, which is not steady in turbulence. Option (a) is not the standard criterion, and option (d) is too general because constant discharge alone does not necessarily define steady turbulent flow.
Heat transfer by radiation mainly depends upon
A)
nature of the body
B)
its temperature
C)
kind and extant of its surface
D)
all of these
Heat transfer by radiation depends on several factors: the nature of the body (its emissivity/absorptivity), its temperature, and the kind and extent of its surface area. Since all these affect radiative heat exchange, the correct answer is 'all of these'.
When heat is transferred by molecular collision, it is referred to as heat transfer by
A)
conduction
B)
convection
C)
radiation
D)
radiation and convection
Heat transfer by molecular collision occurs through direct contact between adjacent molecules, which is called conduction. Convection involves bulk motion of a fluid, while radiation transfers heat by electromagnetic waves and does not require a material medium. Therefore, the correct answer is conduction.