UPPSC Lec'21 ME: Daily Practices Quiz. 09-Nov-2021

Quiz: Mechanical Engineering
Exam: UPPSC AE/Lecturer
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 8 Minutes

Q1. Resilience of a bolt may be increased by
(a) increasing its length
(b) increasing its shank diameter
(c) increasing diameter of threaded portion
(d) increasing head size

Q2. The stream function for a two-dimensional flow is given by ψ=xy. The velocity at (1, 2) is
(a) √5
(b) 5
(c) 2√5
(d) √2

Q3. The temperature of neutral flame in gas welding is (in degree Celsius)
(a) 2900
(b) 3200
(c) 3300
(d) 3840

Q4. The velocity along the tool face plane is known as
(a) Shear velocity
(b) Chip velocity
(c) Cutting velocity
(d) Mean velocity

Q5. For a machine to be overhauling, its efficiency should be
(a) 100 %
(b) Less than 67 %
(c) More than 50 %
(d) Less than 50 %

Q6. Air at 20°C dry bulb temperature and 40% relative humidity is heated upon 40°C using an electric heater, whose surface temperature is maintained uniformly at 45°C. The efficiency of the heater is
(a) 0.80
(b) 0.20
(c) 0.88
(d) 1

Solutions

S1. Ans. (a)
Sol. Resilience of a bolt may be increased by increasing its length.

S2. Ans. (a)
Sol. Given, Stream function ψ=xy
We know that
∂ψ/∂x= v and ∂ψ/∂y=-u
So, u=-∂ψ/∂y=-x=-1 (putting x=1)
v=∂ψ/∂x=y=2 (Putting y=2)
So, the velocity at (1, 2) is √(u^2+v^2 )=√(〖(-1)〗^2+〖(2)〗^2 )=√5

S3. Ans. (a)
Sol.
The temp. in oxidizing flame is generally 3300℃
The temp. in carburizing flame is generally 3100℃
The temp. in neutral flame is generally 2900℃

S4. Ans. (b)
Sol. The velocity along the tool face = chip velocity
The velocity along the shear plane = shear velocity
The velocity in the direction of cutting = cutting velocity.

S5. Ans(d)
Sol. If the efficiency is more than 50%, then the screw is said to be overhauling. Efficiency of self-locking screws is less than 50%.
S6. Ans. (a)
Sol. Given,
t_1=20°C
t_2=40°C
t_3=45°C
BPF=(t_3-t_2)/(t_3-t_1 )=(45-40)/(45-20)=0.2

So, efficiency of the coil is 1-BPF=1-0.2=0.8