Legal Metrology • Mechanical Engineering Paper-I
The fluid forces considered in the Navier Stokes equation are
A)
gravity, pressure and viscous
B)
gravity, pressure and turbulent
C)
viscous, pressure and laminar
D)
gravity, turbulent and viscous
Based on established principles in Mechanical Engineering, the correct and most clinically/technically appropriate choice is 'gravity, pressure and turbulent' (Option B).
Legal Metrology • Mechanical Engineering Paper-I
The refrigerating system of passenger aircraft works on reversed
A)
Brayton cycle
B)
Atkinson cycle
C)
Ericsson cycle
D)
Carnot cycle
Air-cycle refrigeration used in aircraft is the reversed Brayton (Joule) cycle.
Legal Metrology • Mechanical Engineering Paper-I
Thermoelectric refrigeration system is based on
A)
Peltier effect
B)
Joule effect
C)
Joule-Thomson throttling
D)
adiabatic magnetisation
Thermoelectric refrigeration is based on the Peltier effect.
Legal Metrology • Mechanical Engineering Paper-I
The comfort air-conditioning and industrial air conditioning differ in relation to
A)
process adopted
B)
equipment used
C)
indoor requirement
D)
environmental condition
Comfort and industrial air conditioning mainly differ in the required indoor/environmental conditions.
Legal Metrology • Mechanical Engineering Paper-I
Which is usually the costliest item in a refrigeration system?
A)
condenser
B)
capillary tube
C)
compressor
D)
evaporator
The compressor is usually the most expensive major component in a vapor-compression refrigeration system.
Legal Metrology • Mechanical Engineering Paper-I
The height of water column (in meters) corresponding to a pressure equivalent of 75 cm of mercury column is
A)
1.0
B)
1.02
C)
1.04
D)
1.06
1 atm is 76 cm of Hg, which is approx 10.33 m of water. 75 cm of Hg equals roughly 1.02 m of water.
Legal Metrology • Mechanical Engineering Paper-I
Most unsteady heat flow occurs
A)
through the walls of a refrigerator
B)
during annealing of castings
C)
through the walls of a furnace
D)
through insulated pipe carrying steam
Annealing can involve a large transient temperature change, producing strong unsteady heat flow.
Legal Metrology • Mechanical Engineering Paper-I
If mercury in a barometer is replaced by water, the height of 3.75 cm of mercury will be following cm of water
A)
51cm
B)
50cm
C)
52cm
D)
52.2cm
In the context of Mechanical Engineering, the most appropriate and technically accurate answer is '52cm' (Option C).
Legal Metrology • Mechanical Engineering Paper-I
Dew point is the temperature at which the condensation begins when the air is cooled at constant:
A)
volume
B)
entropy
C)
pressure
D)
enthalpy
Dew point is defined by cooling moist air at constant pressure until saturation is reached.
Legal Metrology • Mechanical Engineering Paper-I
In conventional refrigerants, what is the element responsible for ozone depletion?
A)
Chlorine
B)
Fluorine
C)
Carbon
D)
Hydrogen
Chlorine-containing refrigerants can release chlorine radicals that catalytically destroy ozone.
Legal Metrology • Mechanical Engineering Paper-I
For warships, metacentric height of ship should vary between
A)
0-1m
B)
1-2m
C)
5-10m
D)
more than 10m
Based on established principles in Mechanical Engineering, the correct and most clinically/technically appropriate choice is '0-1m' (Option A).
Legal Metrology • Mechanical Engineering Paper-I
Bernoulli equation deals with the law of conservation of
A)
mass
B)
momentum
C)
energy
D)
work
In the context of Mechanical Engineering, the most appropriate and technically accurate answer is 'mass' (Option A).
Legal Metrology • Mechanical Engineering Paper-I
A metallic piece weighs 80 N in air and 60 N in water. The relative density of the metal would be
A)
8
B)
6
C)
4
D)
3
Based on established principles in Mechanical Engineering, the correct and most clinically/technically appropriate choice is '6' (Option B).
Legal Metrology • Mechanical Engineering Paper-I
Fins are made as thin as possible to
A)
reduce the total weight
B)
accommodate more number of fins
C)
increase the width for the same profile area
D)
improve the flow of coolant around the fin
Thin fins allow a greater number of fins and therefore more heat-transfer area within the same volume.
Legal Metrology • Mechanical Engineering Paper-I
An engine operates between temperatures limits of 900 K and T₁, another engine operates between T₁ and 400 K. For both engines to be equally efficient, T₁ should be equal to
A)
600K
B)
625K
C)
650K
D)
700K
Equating Carnot efficiencies: 1 - T1/900 = 1 - 400/T1. Solving yields T1 = 600K.
Legal Metrology • Mechanical Engineering Paper-I
All of the followings are unit of thermal conductivity except
A)
kcal/m.hr.°C
B)
kJ/m.hr.K
C)
W/m.s.K
D)
cal/em.s.°C
W/(m·s·K) is dimensionally wrong for thermal conductivity; the others can be expressed in equivalent conductivity units.
Legal Metrology • Mechanical Engineering Paper-I
An object having 10 kg mass weighs 9.81 kg on a spring balance. The value of ‘g’ at this place is
A)
10 m/sec²
B)
9.81 m/sec²
C)
10.2 m/sec²
D)
9 m/sec²
In the context of Unmapped / long tail, the most appropriate and technically accurate answer is '9.81 m/sec²' (Option B).
Legal Metrology • Mechanical Engineering Paper-I
Which of the following types of impeller vanes are most commonly used in centrifugal type impeller?
A)
forward curved
B)
radial
C)
backward
D)
tangential
In the context of Mechanical Engineering, the most appropriate and technically accurate answer is 'tangential' (Option D).
Legal Metrology • Mechanical Engineering Paper-I
Neglecting changes in potential and kinetic energies, the shaft work during a steady flow process is given by
A)
∫p dv
B)
∫v dp
C)
pv
D)
-Δh
For a steady flow process (neglecting KE and PE), the shaft work is equal to -Δh.
Legal Metrology • Mechanical Engineering Paper-I
Heat transfer takes place as per -
A)
zeroth law of thermodynamics
B)
first law of thermodynamic
C)
second law of the thermodynamics
D)
Kirchoff’s law
The second law gives the direction/possibility of heat transfer, from higher to lower temperature unless work is supplied.
Legal Metrology • Mechanical Engineering Paper-I
For the same tip diameter, axial flow compressor compared to centrifugal compressor offers higher
A)
pressure ratio
B)
mass flow
C)
temperature ratio
D)
speed of rotation
In the context of Mechanical Engineering, the most appropriate and technically accurate answer is 'mass flow' (Option B).
Legal Metrology • Mechanical Engineering Paper-I
Resultant pressure of the liquid in case of an immersed body acts through
A)
centre of gravity
B)
centre of pressure
C)
metacentre
D)
centre of buoyancy
Based on established principles in Mechanical Engineering, the correct and most clinically/technically appropriate choice is 'centre of pressure' (Option B).
Legal Metrology • Mechanical Engineering Paper-I
A jet air-craft is powered by
A)
piston engine
B)
screw propeller
C)
gas turbine
D)
free piston engine
In the context of Mechanical Engineering, the most appropriate and technically accurate answer is 'screw propeller' (Option B).
Legal Metrology • Mechanical Engineering Paper-I
What causes suction of fluid into the gear pump?
A)
when pressure drops during disengagement of teeth at the suction side
B)
when pressure increases during disengagement of teeth at the suction side
C)
when pressure drops during engagement of teeth at the suction side
D)
when pressure increases during engagement of teeth at the suction side
In the context of Mechanical Engineering, the most appropriate and technically accurate answer is 'when pressure drops during disengagement of teeth at the suction side' (Option A).
Legal Metrology • Mechanical Engineering Paper-I
The air standard efficiency of an IC engine is given by (where r = Compression ratio, and γ = Ratio of specific heats)
A)
1-r^γ
B)
1-r^(1-γ)
C)
1-(1/r^(γ-1))
D)
None of these
Air-standard Otto-cycle efficiency η=1−1/r^(γ−1)=1−r^(1−γ).
