Quiz: Mechanical Engineering 06 July 2020

Quiz: Mechanical Engineering
Exam: UPSSSC JE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/3 mark
Time: 10 Minutes

Q1. Frictional losses in the nozzle
(a) reduces the enthalpy of the fluid
(b) increases the enthalpy of the fluid
(c) no effect on enthalpy of the fluid
(d) None of the above
L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q2. The pressure centre is
(a) the centroid of the pressure prism
(b) a point on the line of action of the resultant force
(c) at the centroid of the submerged area
(d) always above the centroid of the area
L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q3. Match List-I (Stability) and List-II (Conditions) and select the correct answer using the codes given below the lists:
List-I
A. Stable equilibrium of a floating body
B. Stable equilibrium of a submerged body
C. Unstable equilibrium of a floating body
D. Unstable equilibrium of a submerged body
List-II
1. Centre of buoyancy below the centre of gravity
2. Metacentre above the centre of gravity
3. Centre of buoyancy above the centre of gravity
4. Metacentre below the centre of gravity
Codes:
A B C D
(a) 4 3 2 1
(b) 2 3 4 1
(c) 4 1 2 3
(d) 2 1 4 3
L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q4. Which phenomenon will occur when the valve at the discharge end of a pipe connected to a reservoir is suddenly closed?
(a) Cavitation
(b) Erosion
(c) Hammering
(d) Surging
L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q5. When a system reaches the state of equilibrium, the following property assumes its maximum value
(a) Availability
(b) Entropy
(c) Gibbs function
(d) Helmholtz function
L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q6. In centrifugal compressor terminology, vaneless space refers to the space between
(a) The inlet and blade inlet edge
(b) Blades in the impeller
(c) Diffuser exit and volute casing
(d) Impeller tip and diffuser inlet edge
L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q7. In a single-stage open-cycle gas turbine, the mass flow through the turbine is higher than the mass flows through compressor, because
(a) the specific volume of air increases by use of intercooler
(b) the temperature of air increases in the reheater
(c) the combustion of fuel takes place in the combustion chamber
(d) the specific heats at constant pressure of incoming air and exhaust gases are
different
L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q8. For the same type of shapes, the value of Radiation Shape Factor will be higher when surfaces are
(a) More closer only
(b) Moved further apart
(c) Smaller and held closer
(d) Larger and held closer
L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q9. In aircraft, air refrigeration cycle is used because of
(a) low unit weight per tonne of refrigeration
(b) high heat transfer rate
(c) lower temperature at thigh-altitudes
(d) higher coefficient of performance
L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

Q10. The optimum effective temperature for human comfort is
(a) higher in winter than that in summer
(b) lower in winter than that in summer
(c) same in winter and summer
(d) not dependent on season
L1Difficulty 3
QTags Mechanical
QCreator Paper Maker 10

SOLUTIONS

S1. Ans (a)
Sol. Frictional losses in the nozzle reduces the enthalpy of the fluid.

S2. Ans (b)
Sol. The center of pressure is the point on a body where the total sum of a pressure field acts, causing a force and no moment about that point.

S3. Ans (b)
Sol.
(a) Stable equilibrium of floating body: Metacentre above the centre of gravity.
(b) Stable equilibrium of submerged body: Centre of buoyancy above the centre of gravity.
(c) Unstable equilibrium of a body floating: Metacentre below the centre of gravity.
(d) Unstable equilibrium of a submerged body: Centre of buoyancy below the centre of gravity.

S4. Ans (c)
Sol. When water flowing in a long pipe is suddenly brought to rest by c losing the valve or by any similar cause there will be a sudden rise in pressure due to momentum of the moving water being destroyed this causes a wave of high pressure to be transmitted along the pipe which creates noise called as knocking. This phenomenon of sudden rise in pressure in the pipe is called as water hammer or hammer blow.

S5. Ans (b)
Sol. When system reaches equilibrium, driving force that executed the process becomes zero and entropy attains its maximum value. Moreover as the process progress towards equilibrium the available energy or availability decreases continuously.

S6. Ans (d)
Sol. In centrifugal compressor terminology, vaneless space refers to the space between Impeller tip and diffuser inlet edge.

S7. Ans (c)
Sol. After the compression of air, same amount of fuel is added in the combustion chamber which undergoes combustion. After combustion the flue gases are expanded in the turbine which is more than the mass flow rate of only air in the compressor.

S8. Ans(d)
Sol. The value of radiation shape factor is high if surfaces are large and closer to each other.

S9. Ans.(a)
Sol. In aircraft, air refrigeration cycle is used because of low unit weight per ton of refrigeration. It is becoming obsolete because of their low coefficient of performance and high power requirements.

S10. Ans.(b)
Sol. In winter the optimum effective temperature is 19°C where as in summer this temperature is 22°C.

Leave a comment

Your email address will not be published. Required fields are marked *