UPPSC Lec’21 ME: Daily Practices Quiz. 11-Oct-2021

Quiz: Mechanical Engineering
Exam: UPPSC Lecturer
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 6 Minutes

Q1. The gas turbine which is used in an aircraft is
(a) Constant temperature turbine
(b) Open cycle turbine
(c) Closed cycle turbine
(d) None of these

Q2. The type of compressor which is used in vapour compression refrigeration system for more than 100 tonnes capacity is
(a) Reciprocating compressor
(b) Centrifugal compressor
(c) Rotary compressor
(d) Both (a) and (b)

Q3. The type of flow in convergent divergent nozzle in which the Mach number is 6
(a) Hypersonic
(b) Subsonic
(c) Supersonic
(d) Sonic

Q4. Critical activities
(a) Is longest path
(b) Is shortest path
(c) Has zero float
(d) Both (a) and (c)

Q5. Which of the following behaviour 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.

Q6. Force F in the given figure equals to

(a) √3 kN
(b) 2 kN
(c) – √3 kN
(d) 3√3 kN

Solutions

S1. Ans. (b)
Sol. The gas turbine which is used in an aircraft is open cycle turbine.
In this cycle the gas is released from the turbine to the surroundings

S2. Ans. (b)
The type of compressor which is used in vapour compression refrigeration system for more than 100 tonnes capacity is Centrifugal compressor and the type of compressor which is used in vapour compression refrigeration system for less than 100 tonnes capacity is reciprocating compressor

S3. Ans. (a)
Sol.
Mach Number Type of Flow
Mach No. < 0.8 Sub-sonic
0.8 < Mach No. < 1.3 Trans-sonic
Mach No. = 1 Sonic
1.3 < Mach No. < 5 Super-sonic
Mach No. > 5 Hypersonic

S4. Ans (d)
Sol. Critical activities are those activities whose float is zero and has longest path.

S5. Ans.(d)
Sol. ς=c/(2mω_n )<1
This condition is known as under-damping, as under damping system does simple harmonic motion.
In underdamped system, amplitude of vibration decreases slowly in exponential manner.
Displacement at any instant of time for under damped system is given by ▭(x=Ae^(- ςω_n t) (sin⁡( ςω_n t)+ϕ) )

S6. Ans.(a)
Fig.

Sol. from lami’s theorem
1/sin⁡150 = F/sin⁡〖60°〗
F = sin⁡〖60°〗/sin⁡〖150°〗
F = √3 N

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