Quiz:Mechanical Engineering 17.4.2020

Quiz: Mechanical Engineering
Exam: NLC (GET)
Topic: Miscellaneous

Each question carries 1 mark.
Negative marking: 1/4 mark
Time: 10 Minute

Q1. If there is an alien planet, on which there is no atmosphere then by which process heat transfer can take place from a hot body to an astronomer.
(a) Radiation and convection
(b) Only radiation
(c) Only convection
(d) Conduction, convection and radiation

L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q2. If there is a closed insulated system and irreversible work is transferred into the system then it can be said that
(a) Entropy will be generated
(b) Entropy will be transferred
(c) Enthalpy will decrease
(d) None of the above

L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q3. If inertia force is doubled and viscous force is increased by a factor √2 then Grashoff‘s number will be
(a) Double
(b) 1.41 times
(c) Remain same
(d) 1.2 times

L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q4. If in a fuel, Iso-octane is 80% by volume then the Octane number of fuel is
(a) 20
(b) 80
(c) 60
(d) 40

L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q5. A Worm and worm wheel drive has pressure angle of gear 30° then find out the maximum efficiency of gear drive
(a) 33%
(b) 50%
(c) 60%
(d) 66%

L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q6. We know CO2 and Argon mixture is used in Metal inert gas welding, we use CO2 to
(a) Improve weld surface finish
(b) Increase weld penetration
(c) Stabilize arc
(d) Reduce weld spatter

L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q7. In stainless steel, a very useful alloying element is mixed to prevent its corrosion for a long time by providing a thin anti rust film on stainless steel equipment. This element will have which type of crystal structure?
(a) BCC
(b) FCC
(c) HCP
(d) SC

L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q8. The primary function of the flywheel is:
(a) To limit the fluctuations of speed during each cycle
(b) To absorb energy during these periods of crank rotation when turning moment is less than the resisting points
(c) To maintain the constant speed of rotation of the crankshaft when the load on the engine increases
(d) To maintain constant speed of rotation of the crank shaft when the load on the engine decreases

L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q9. Which of the following behavior of the system defines under-damped harmonic oscillator?
(a) The system returns (exponentially decays) to equilibrium without oscillating
(b) The system returns to equilibrium as quickly as possible without oscillation.
(c) The system oscillates (at reduced frequency compared to the undamped case) with the amplitude gradually decreasing to zero.
(d) The system oscillates at its natural resonant frequency.

L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q10. Which one of the following statements applicable to a perfect gas will also be true for an irreversible process?
(a) δQ=dU+PdV
(b) δQ=TdS
(c) TdS=dU+PdV
(d) None of these

L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Solutions

S1. Ans (b)
Sol. As radiation process does not require any medium for heat transfer from a body to another body .so, without atmosphere; heat can be transferred from a hot body to a man by radiation process.

S2. Ans (a)
Sol. Entropy can be generated by only by irreversible work transfer. Entropy change or transfer can take place by heat transfer.
Irreversible work generates entropy because it involves a gradient in some field (e.g., pressure, force, electric field, etc.). When this gradient drives a transfer of energy, entropy is created.

S3. Ans (c)
Sol. We know,
Grashoff’s No.=(Inertia Force X Buoyancy  Force)/[Viscous Force]^2
=2/2
=1

S4. Ans (b)
Sol. Octane Number is defined as the value of Iso-octane by volume in the mixture of fuel.
Here, it is 80%. Hence, Octane No. is 80.

S5. (a)
Sol. We know,
Maximum Efficiency of worm and worm wheel (η_max)=(1-sinφ)/(1+sinφ)
Given,
φ=30°
Hence,
(η_max)=(1-sin30)/(1+sin30)
η_max=0.33 or 33%

S6. Ans.(b)
Sol. CO2 added in MIG welding to increase deep weld penetration and used in mixture with Argon.

S7. Ans.(a)
Sol. Chromium is added in stainless steel which is corrosion resistant.
Cr has Body centered cubic structure (BCC).

S8. Ans.(a)
Sol. A flywheel is a device which resists the fluctuation of speed of engine during each cycle of engine due to its inertia.
It stores excess energy and also provide energy to engine wheels when there is requirement of more energy.
Max fluctuation of energy(∆E=I.w^2.k)

S9. Ans.(d)
Sol. In under-damped system, amplitude of vibration decreases slowly in exponential manner.

S10. Ans (c)
Sol. TdS=dU+PdV
This equation consists of only point functions, so it is valid for all processes and also for perfect gas.

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