Quiz: Mechanical Engineering 07 May 2020

Quiz: Mechanical Engineering
Exam: UPPSC AE
Topic: Miscellaneous

Each question carries 3 mark.
Negative marking: 1 mark
Time: 10 Minute

Q1. A flow chart that outlines the main segment of any program
(a) Micro
(b) Queue
(c) Macro
(d) Union

Q2. Queuing theory is associated with
(a) Production time
(b) Waiting time
(c) Planning time
(d) Sales time

Q3. A taper provided on the pattern for its easy and clean withdrawal from the mould is known as
(a) Shrinkage allowance
(b) Machining allowance
(c) Distortion allowance
(d) Draft allowance

Q4. A body is subjected to a direct tensile stress of 300 MPa in one plane accompanied by a simple shear stress of 200 MPa. The maximum shear stress will be
(a) 150 MPa
(b) 200 MPa
(c) 250 MPa
(d) 300 MPa

Q5. The short-coming of first law of thermodynamics is
(a) Direction of process
(b) Possibility of process
(c) Quality of process
(d) Quantity of process

Q6. Carnot cycle efficiency is maximum when
(a) Initial temperature is 0 K
(b) Final temperature is 0 K
(c) Initial temperature is 0 deg C
(d) Final temperature is 0 deg C

Q7. For an ideal gas enthalpy is represented by
(a) H=U-RT
(b) H=U+RT
(c) H=RT-U
(d) H=-(U+RT)

Q8. For an infinitely long fin, efficiency is given by
(a) 1/(mL)
(b) 2/(mL)
(c) 1/(2mL)
(d) 3/(mL)

Q9. Which fluid does not experience stress during flow?
(a) Dilatant
(b) Bingham-plastic
(c) Visco-plastic
(d) Inviscid

Q10. Normalizing is best suited for which material?
(a) Low and medium carbon steel
(b) High carbon steel
(c) Cast iron
(d) Steel wires and plates

Solutions

S1. Ans.(c)
Sol. Macro flow chart shows the major steps of any program. Micro flowchart shows all the details necessary to capture exactly how a process is done.

S2. Ans.(b)
Sol. Queuing theory is associated with waiting time and service time. It is used to cater many real-life processes to reduce time of operation and improve its efficiency. E.g. Aerospace industry, process industry, restaurants, E-commerce etc.

S3. Ans.(d)
Sol. Draft allowance are provided on the sides of pattern for the easy removal of pattern without tearing the casting mould.

S4. Ans.(c)
Sol. Maximum shear stress =√((σ/2)^2+τ^2 )…………(1)
Given,
σ=300 MPa
τ=200 MPa
From equation (1)
Maximum shear stress =√((300/2)^2+(200)^2 )
Maximum shear stress=250 MPa

S5. Ans.(a)
Sol. First law of thermodynamics does not tell about the direction of the heat transfer. It is the limitation of the first law of thermodynamics.

S6. Ans.(b)
Sol. According to Kelvin-Plank statement of Second law of thermodynamics, efficiency of the Carnot cycle is maximum when the system during a thermodynamic process attains absolute zero temperature 0 K.
If a system attains absolute zero temperature 0 K then Carnot cycle efficiency will be 100%.

S7. Ans.(b)
Sol. For an ideal gas Enthalpy H=U+PV
But from ideal gas equation- PV=RT, for (mass (m) = 1 kg)
Hence, H=U+RT

S8. Ans.(a)
Sol. Efficiency of a fin is the ratio of actual heat transfer from the fin to the maximum possible heat transfer from the fin.
For infinitely long fin η=1/(mL)
Here, m=√(Ph/KA)
P = Perimeter of fin cross section
h=coefficient of heat transfer
K = thermal conductivity of fin material
A = cross-section area of fin

S9. Ans.(d)
Sol. As, no resistance induced between layers of non-viscous fluid flow. Hence, shear stress is zero in inviscid fluid flow.

S10. Ans.(a)
Sol. Normalizing involves heating a material to an elevated temperature and then allowing it to cool back to room temperature by exposing it to room air. Normalizing is a heat treatment process that is used to make a metal more ductile and tough at the core and hard at the surface. It is best suited for low and medium carbon steel.

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