Quiz:Mechanical Engineering 25 May 2020

Quiz: Mechanical Engineering
Exam: UPSSSC JE
Topic: Miscellaneous

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

Q1. Curtis turbine is
(a) Reaction steam turbine
(b) Pressure velocity compounded impulse turbine
(c) Pressure compounded impulse steam turbine
(d) Velocity compounded impulse steam turbine

Q2. Piston rings are generally made of the following material.
(a) Cast iron
(b) mild steel
(c) aluminium
(d) carbon steel

Q3. In a four-stroke SI engine, the cam shaft runs at
(a) same speed as crankshaft
(b) half the speed of crankshaft
(c) twice the speed of crankshaft
(d) any speed irrespective of the crankshaft

Q4. If the capacity of a refrigeration machine is 2 ton, then the rate of heat abstraction is equal to
(a) 50 Kcal/min
(b) 100 Kcal/min
(c) 150 Kcal/min
(d) 500 Kcal/min

Q5. Which of the following components of vapour absorption refrigeration system has same pressure level (neglecting the pipe loss)?
(a) Generator and absorber
(b) Evaporator and absorber
(c) Generator and evaporator
(d) Condenser and evaporator

Q6. The radial heat transfer rate through hollow cylinder increases as the ratio of outer radius to inner radius-
(a) decreases
(b) increases
(c) constant
(d) decreases as well as increases

Q7. The center of buoyancy in case of heavy object when immersed in a liquid completely, will be at
(a) The center of gravity of the object
(b) The center of gravity of the volume displaced
(c) Above the center of gravity of the object
(d) Below the center of gravity of object

Q8. If a particle is in static equilibrium, then the work done by the system of force acting on that particle is:
(a) Negative
(b) Infinity
(c) Zero
(d) Positive

Q9. The area (per unit volume) under the stress-strain curve up to the point of rupture is known as
(a) Proof resilience
(b) Modulus of toughness
(c) Modulus of elasticity
(d) Modulus of resilience

Q10. Which one of the following is not a desirable characteristics of friction clutches?
(a) The moving parts should be weight enough
(b) Should have good thermal conductivity
(c) Should have high coefficient of friction
(d) Should have high wear resistance

Solutions

S1. Ans.(d)
Sol. Curtis turbine is a velocity compounded impulse steam turbine. In which high velocity steam energy, exiting from nozzle, is made to consume in moving runner blades in parts.

S2. Ans.(a)
Sol. The material of Piston rings should be wear-resistant and heat-resistant. So, Piston rings are made of cast iron.

S3. Ans.(b)
Sol. It depends on the fact whether the engine is four-stroke or two-stroke. A camshaft on a four-stroke engine runs at half the crankshaft speed, the intake and exhaust valves open once (each) for each two engine revolutions. Similarly, in a two-stroke engine, it is one to one.

S4. Ans.(b)
Sol. We know that
1 ton = 210 kJ/min
1 kJ = 4.18 kcal
Heat extraction from 2-ton refrigeration unit = (2×210)/4.18=100.47 kcal/min or 100 kcal/min

S5. Ans.(b)
Sol. Both evaporator and absorber have same level of pressure if we neglect piping friction losses in vapour absorption refrigeration system.

S6. Ans.(a)
Sol. We know that
Heat transfer rate for a hollow cylindrical object across its wall is given by the following expression,
Q=(2πkL(T2-T1))/(ln⁡(r2/r1))
If r2/r1 ↓,then Q↑.

S7. Ans.(b)
Sol. According to Archimedes’ principle, if a body is completely submerged in a liquid then buoyancy force acting on the body will be equal to the weight of the liquid displaced and it acts at the center of gravity of the liquid displaced.

S8. Ans.(c)
Sol. If a particle is in static equilibrium then it means that the body has its linear momentum as well as angular momentum conserved. Hence, net force acting on the body will be zero.

S9. Ans.(b)
Sol. The area (per unit volume) under the stress-strain curve up to the point of rupture (failure point) is known as modulus of toughness.

S10. Ans.(a)
Sol. Desirable characteristics of friction clutches:
1.It should not have enough weight.
2.It should have high thermal conductivity.
3.It should have high coefficient of friction.
4.It should have high wear resistance.

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