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# UPRVUNL’21 ME: Daily Practices Quiz. 11-Aug-2021

Q1. An oil of specific gravity 0.9 has viscosity of 0.28 stokes at 38°C. What will be its viscosity in Ns/m²?
(a) 0.2520
(b) 0.0311
(c) 0.0252
(d) 0.0206

Q2. What is the pressure difference between inside and outside of a droplet of water?
(a) 2σ/d
(b) 4σ/d
(c) 8σ/d
(d) 12σ/d
Where σ is surface tension and d is the diameter of the droplet.

Q3. Resultant pressure of the liquid in case of an immersed body acts through which one of the following?
(a) Centre of gravity
(b) Centre of pressure
(c) Metacentre
(d) Centre of buoyancy

Q4. A house-top water tank is made of flat plates and is full to the brim. Its height is twice that of any side. The ratio of total thrust force on the bottom of the tank to that on any side will be:
(a) 4
(b) 2
(c) 1
(d) 0.5

Q5. Consider the following statements:
1. The increase in metacentric height
2. Increases stability
3. Decreases stability
4. Increases comfort for passengers in a ship
5. Decreases comfort for passengers in a ship
Which of the above statements are correct?
(a) 1 and 3
(b) 1 and 4
(c) 2 and 3
(d) 2 and 4

Q6. A streamline is a line
(a) which is along path of the particle
(b) which is always parallel to the main direction of flow
(c) along which there is no flow
(d) on which tangent drawn at any point gives the direction of velocity

Solutions
S1. Ans (c)
Sol. Dynamic viscosity,
μ=ρυ=(0.9×1000)×(0.28×10^(-4) )
=0.0252 Ns/m²

S2. Ans (b)
Sol. Pressure difference between inside and outside of a droplet of water = 4σ/d
∵ Bursting force = p×πd²/4
Resisting force = σ ×π d
Bursting force= Resisting force
p×πd²/4=σ×πd
or p=4σ/d

S3. Ans (b)
Sol. The point of application of resultant pressure is called as centre of pressure.

S4. Ans (c)
Sol.

S5. Ans (b)
Sol. Time period of oscillations is inversely proportional to meta centric height. Thus, more the GM less will be time period, and body regains its position in less time. So more stable.

S6. Ans (d)
Sol. A stream line is a line on which tangent drawn at any point gives the direction of velocity.

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