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# UPPSC Lec’21 ME: Daily Practices Quiz. 28-Sep-2021

### UPPSC Lec’21 ME: Daily Practices Quiz. 28-Sep-2021

Quiz: Mechanical Engineering
Exam: UPPSC Lecturer
Topic: Miscellaneous

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

Q1. The damping ratio in case of critical damping is…………………….
(a) Equal to one
(b) Equal to zero
(c) Less than one
(d) Greater than one

Q2. A differential gear in an automobile is a
(a) simple gear train
(b) epicyclic gear train
(c) compound gear train
(d) speed reducer

Q3. The intensity of pressure at a depth h is equal to
(a) specific weight × depth
(b) specific volume × depth
(c) density × depth
(d) force depth

Q4. In PERT and CPM network the dummy activity
(a) consumes time
(b) consumes resources
(c) is used to preserve the logic
(d) is a real activity

Q5. Why are surge tanks used in pipe line?
(a) To reduce frictional loss in pipe
(b) To ensure uniform flow in pipe
(c) To relieve the pressure due to water hammer
(d) To reduce cavitation

Q6. Air is flowing over a flat plate with a free steam velocity of 24 m/s, and its kinematic viscosity is 72×10^(-6) If a particular point, the Reynolds number is 30000, its location from the leading edge is.
(a) 0.05 m
(b) 0.07 m
(c) 0.08 m
(d) 0.09 m

### Solutions

S1. Ans. (a)
Sol Damping factor is the ratio of damping coefficient (c) and critical damping coefficient (Cc)
Damping factor, ς=C/c_c
ς = 1, critically damped system
ς > 1, over damped system

S2. Ans. (b)
Sol. differential gear mechanism works on the principle of epicycle gear train.

When the car is on a straight road, the ring gear, differential cage, differential pinion gear and two differential side gears all tum as a unit. The two differential pinion gears do not rotate on the pinion shaft; therefore, they exert equal force on the two differential side gears. As a result, the side gears turn at same speed as the ring gear, which causes both the drive wheels to turn at same speed. However, when the car begins to round a curve, the differential pinion gears rotate on the pinion shaft. This permits the outer wheel to turn faster than the inner wheel.

S3. Ans.(a)
Sol. P = (ρg) h
= specific weight × height

S4. Ans.(c)
Sol. In PERT and CPM network the dummy activity is used to preserve the logic

S5. Ans.(c)
Sol.
Surge tank is an open reservoir provided in between penstock to
(i) absorb the pressure wave due to sudden blockage of flow in the turbine which will reduce water pressured hammer problem
(ii) to serve for emergency supply and to maintain constant head at inlet of turbine

S6. Ans.(d)
Sol.
Re=ux/ϑ
x=(30000×72×10^(-6))/24=0.09 m=9 cm

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