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

Quiz: Mechanical Engineering
Exam: UPPSC AE/Lecturer
Topic: Fluid Mechanics

Each question carries 3 marks
Negative marking: 1 mark
Time: 8 Minutes

Q1. In case of a differential manometer, a head of 1.5m of an oil in limb A is found to balance a head of 0.75 m of different oil in limb B. The ratio of specific gravities of oil in limb A to B is
(a) 2
(b) 0.5
(c) 3
(d) 0.15

Q2. Generally, the high vacuum pressure is expressed in
(a) Pascal
(b) mm of water
(c) Torr
(d) cm of water

Q3. The atmospheric pressure at sea level is 100000 N/m^2. What will be the absolute pressure at the height of 3 km above the sea level? [Assume the pressure variation follow hydrostatic law, also assume the density of air is 1.2 kg/m^2 and g=10m/s^2]
(a) 6.4 N/m^2
(b) 16 N/〖cm〗^2
(c) 8.0 N/〖cm〗^2
(d) 6.4 N/〖cm〗^2

Q4. McLeod gauges are used for measuring
(a) RPM of shaft
(b) Surface roughness
(c) Vacuum
(d) Velocity

Q5. A container which carries water is moving in a horizontal direction with an acceleration of 17.32 m/s^2 The approx. angle of inclination of free water surface to the horizontal is
(a) 60°
(b) 30°
(c) 45°
(d) 0°

Q6. The necessary and sufficient condition for bodies in flotation to be in stable equilibrium is that the centre of gravity is located below the
(a) Metacentre
(b) Centre of buoyancy
(c) Epicenter
(d) Centroid

Solutions

S1. Ans. (b)
Sol. Given that, head of 1.5m of an oil in limb A = Head of 0.75 m of another fluid in limb B
Let S_A and S_B are the specific gravities of oil in limb A and limb B respectively.
So, S_A h_A=S_B h_B
S_A×1.5=S_B×0.75
S_A/S_B =0.75/1.5=1/2
S2. Ans. (c)
Sol. Generally, the high vacuum pressure is expressed in Torr.
And, we know that, 1 Torr=133.32 Pa

S3. Ans. (d)
Sol. P_abs=P_abs- ρgh
P_abs=100000-1.2×10×3000
P_abs=64000N/m^2
P_abs=6.4 N/〖cm〗^2
S4. Ans. (c)
Sol. McLeod gauges are generally used for measuring vacuum.
A McLeod gauge is a scientific instrument which is used to measure very low pressures near about 10^(-6) torr.

S5. Ans. (a)
Sol.
tanθ =a/g
tanθ=17.32/10
tanθ=1.732
tanθ=√3
θ=60°

S6. Ans. (a)
Sol. The necessary and sufficient condition for stable equilibrium of floating bodies, metacentre is above centre of gravity.
Metacentre above centre of gravity means it is the case of stable equilibrium
Metacentre coincides centre of gravity means it is the case of Neutral equilibrium
Metacentre below centre of gravity means it is the case of unstable equilibrium

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