Mechanical Properties of Fluids Questions and Answers Part-14

1. Due to capillary action, a liquid will rise in a tube, if the angle of contact is
a) Acute
b) Obtuse
c) 90°
d) Zero

Answer: a

2. In the state of weightlessness, a capillary tube is dipped in water, then water
a) Will not rise at all
b) Will rise to same height as at atmospheric pressure
c) Will rise to less height than at atmospheric pressure
d) Will rise up to the upper end of the capillary tube of any length

Answer: d
Explanation: In the state of weightlessness or in gravity free space, water will rise to the upper end of the tube of any length

3. Two parallel glass plates are dipped partly in the liquid of density 'd' keeping them vertical. If the distance between the plates is 'x', surface tension for liquids is T and angle of contact is \[\theta\] , then rise of liquid between the plates due to capillary will be
a) \[\frac{T\cos\theta}{xd}\]
b) \[\frac{2T\cos\theta}{xdg}\]
c) \[\frac{2T}{xd g\cos\theta}\]
d) \[\frac{T\cos\theta}{xdg}\]

Answer: b
Let the width of each plate is b and due to surface tension liquid will rise upto height h then upward force due to surface tension = 2Tb cos\[\theta\] …(i)
Weight of the liquid rises in between the plates

4. Water rises in a capillary tube to a certain height such that the upward force due to surface tension is balanced by \[75\times 10^{-4} N\]   force due to the weight of the liquid. If the surface tension of water is \[6\times 10^{-2} Nm^{-1}\]   , the inner circumference of the capillary must be
a) \[1.25\times 10^{-2} m\]
b) \[0.50\times 10^{-2} m\]
c) \[6.5\times 10^{-2} m\]
d) \[12.5\times 10^{-2} m\]

Answer: d

5. It is not possible to write directly on blotting paper or newspaper with ink pen
a) Because of viscosity
b) Because of inertia
c) Because of friction
d) Because of capillarity

Answer: d
Explanation: Due to capillarity it absorbs the ink

6.Two capillary tubes P and Q are dipped in water. The height of water level in capillary P is 2/3 t the height in Q capillary. The ratio of their diameters is
a) 2 : 3
b) 3 : 2
c) 3 : 4
d) 4 : 3

Answer: b

7. Two capillaries made of same material but of different radii are dipped in a liquid. The rise of liquid in one capillary is 2.2 cm and that in the other is 6.6 cm. The ratio of their radii is
a) 9 : 1
b) 1 : 9
c) 3 : 1
d) 1 : 3

Answer: c

8. Two capillaries made of the same material with radii \[r_{1}=1mm\]   and \[r_{2}=2mm\]   . The rise of the liquid in one capillary \[\left(r_{1}=mm\right)\]   is 30 cm, then the rise in the other will be
a) 7.5 cm
b) 60 cm
c) 15 cm
d) 120 cm

Answer: c

9. When a capillary is dipped in water, water rises to a height h . If the length of the capillary is made less than h , then
a) The water will come out
b) The water will not come out
c) The water will not rise
d) The water will rise but less than height of capillary

Answer: b
Explanation: The water will not come out

10. Water rises upto 10 cm height in a long capillary tube. If this tube is immersed in water so that the height above the water surface is only 8 cm, then
a) Water flows out continuously from the upper end
b) Water rises upto upper end and forms a spherical surface
c) Water only rises upto 6 cm height
d) Water does not rise at all

Answer: b
Explanation: Water rises upto upper end and forms a spherical surface