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Ajneesh

HomeAuthor: AjneeshPage 8

13. A spherical drop of oil of radius 1 cm is broken into 1000 droplets of equal radii. If the surface tension of oil is 50 dynes/cm, the work done is

(a)  18 π ergs (b)  180 π ergs (c)  1800 π ergs (d)  8000 π ergs Ans. c (6)

12. If work W is done in blowing a bubble of radius R from a soap solution, then the work done in blowing a bubble of radius 2R from the same solution is

(a)  W/2 (b)  2W (c)   4W (d) (7/3) W Ans. c (33)

11. The surface tension of a liquid is 5 N/m. If a thin film of the area 0.02 m2 is formed on a loop, then its surface energy will be

(a)    5 x 102 j (b)  2.5  x 10-2 j (c)    2 x 10-1 (d)  5 x 10-1 j...

9. If T is the surface tension of soap solution, the amount of work done in blowing a soap bubble from a diameter D to 2D is

(a)  2  πD2T (b)  4 πD2T (c)   6  πD2T (d)  8 πD2T Ans. c (11)

8. The amount of work done in blowing a soap bubble such that its diameter increases from d to D is (T= surface tension of the solution)

(a) 4π(D2-d2)T (b) 8π(D2-d2)T (c) π(D2-d2)T (d) 2π(D2-d2)T Ans. d (8)

7. A spherical liquid drop of radius R is divided into eight equal droplets. If surface tension is T, then the work done in this process will be

(a)  2  πR2T (b)  3 πR2T (c)  4  πR2T (d)  2 πR2T Ans. c (32)

6. Work done in splitting a drop of water of 1 mm radius

into 106 droplets is (Surface tension of water= 72 x 10-3 J/m2 (a) 9.58 x 10-5 j (b) 8.95 x...

1. Energy needed in breaking a drop of radius R into n drops of radii r is given by

(a) 4πT(nr2-R2) (b) (4/3)π(r3n-R2) (c)  4πT(R2-nr2) (d) 4πT(nr 2 + R2) Ans.a (5)

2. The potential energy of a molecule on the surface of liquid compared to one inside the liquid is

(a)  Zero (b)  Smaller (c)   The same (d)  Greater Ans. d (9)

3. Two droplets merge with each other and forms a large droplet. In this process

(a)  Energy is liberated (b)  Energy is absorbed (c)   Neither liberated nor absorbed (d)  Some mass is converted into energy...

4. A drop of liquid of diameter 2.8 mm breaks up into 125 identical drops. The change in energy is nearly (S.T. of liquid =75 dynes/cm)

(a)  Zero (b)  19 erg (c)   46 erg (d)  74 erg Ans. d (4)

16. If the surface of a liquid is plane, then the angle of contact of the liquid with the walls of container is

(a)  Acute angle (b)  Obtuse angle (c)  90° (d)  0° Ans. (d) Tangent drawn at point of contact makes 0°...

15. For which of the two pairs, the angle of contact is same

(a)  Water and glass; glass and mercury (b) Pure water and glass; glass and alcohol (c)   Silver and water; mercury...

14. What is the shape when a non-wetting liquid is placed in a capillary tube

(a)  Concave upward (b)  Convex upward (c)  Concave downward (d)  Convex downward Ans. (b) Since for such liquid (Non-wetting) angle...

13. A liquid wets a solid completely. The meniscus of the liquid in a sufficiently long tube is

(a)  Flat (b)  Concave (c)   Convex (d)  Cylindrical Ans. b (7)

12. Nature of meniscus for liquid

of 00 angle of contact (a)  Plane (b)  Parabolic (c)  Semi-spherical (d) Cylindrical   Ans. c (11)

11. The value of contact angle for kerosene with solid surface.

(a)  0° (b) 900 (c)  450 (d) 330 Ans. a (35)

9. The liquid meniscus in capillary tube will be convex, if the angle of contact is

(a)  Greater than (b)  Less than 90° (c)   Equal to 90°                                 (d)  Equal to 0° Ans. a (4)

8. A glass plate is partly dipped vertically in the mercury and the angle of contact is measured. If the plate is inclined, then the angle of contact will

(a)   Increase (b)  Remain unchanged (c)   Increase or decrease (d)   Decrease Ans. b (7)

5. The excess pressure due to surface tension in a spherical liquid drop of radius r is directly proportional to

(a)  r (b) r2 (c)     r-1 (d) r-2 Ans. c (8)

4. When two soap bubbles of radius

r1 and r2(r2>r1) coalesce, the radius of curvature of common surface is (a)    r2-r1 (b)  r2-r1/r1r2 (c)  r1r2/ r2-r1 (d)...

3. The surface tension of soap solution is

25 x 10-3 Nm-1 .  The excess pressure inside a soap bubble of diameter 1 cm is            (a)   10...

9. The pressure of air in a soap bubble of 0.7cm diameter is 8 mm of water above the pressure outside. The surface tension of the soap solution is

(a) 100 dyne/cm (b) 68.66 dyne/cm (c)  137  dyne/cm (d) 150 dyne/cm Ans. b (51)

7. If the surface tension of a soap solution is 0.03 MKS units, then the excess of pressure inside a soap bubble of diameter 6 mm over the atmospheric pressure will be

(a) Less than 40 N/m2                             (b) Greater than 40 N/m2 (c)   Less than 20 N/m2                  (d) Greater than 20 N/m2...

8. The excess of pressure inside a soap bubble than that of the outer pressure is

(a)  2T/r (b)  4T/r (c)  T/2r (d) T/r Ans. b (6)

14. When a large bubble rises from the bottom of a lake to the surface, its radius doubles. If atmospheric pressure is equal to that of column of water height H, then the depth of lake is

(a)      H     (b)   2H (c)   7H                                      (d)  8H Ans. c (3)

13. The adjoining diagram shows three soap bubbles

A, B and C prepared by blowing the capillary tube fitted with stop cocks, S1, S2 and S3. With stop...

12. The radii of two soap bubbles

are r1 and r2. In isothermal conditions, two meet together in vaccum. Then the radius of the resultant bubble is...

11. A capillary tube of radius r is dipped in a liquid of density ρ and surface tension S. If the angle of contact is θ, the pressure difference between the two surfaces in the beaker and the capillary

(a)(S/r) cos θ (b) (2S/r) cos θ (c)  S/r cos θ (d)  2S/r cos θ Ans. b (8)

10. Pressure inside two soap bubbles are 1.01 and 1.02 atmospheres. Ratio between their volumes is

(a)   102 : 101 (b)  (102)3 : (101)3 (c)   8 : 1 (d)  2 : 1 Ans. c (27)

17. Excess pressure of one soap bubble is four times more than the other. Then the ratio of volume of first bubble to another one is

(a)  1 : 64 (b)  1 : 4 (c)   64 : 1 (d)  1 : 2 Ans. a (9)

16. The volume of an air bubble becomes three times as it rises from the bottom of a lake to its surface. Assuming atmospheric pressure to be 75 cm of Hg and the density of water to be 1/10 of the density of mercury, the depth of the lake is

(a)  5 m                                     (b) 10 m (c) 15 m                                          (d) 20 m Ans. c (13)

15. A soap bubble in vacuum has a radius of 3 cm and another soap bubble in vacuum has a radius of 4 cm. If the two bubbles coalesce under isothermal condition, then the radius of the new bubble is

(a)  2.3 cm                                        (b)  4.5 cm (c)   5 cm                                   (d) 7 cm Ans. c (41)

21. A spherical drop of water has radius 1 mm If surface tension of

water is 70 x 10-3 N/m difference of pressures between inside and out side of the spherical drop is (a) ...

5. A mercury drop does not spread on a glass plate because the angle of contact between glass and mercury is

(a)      Acute (b)  Obtuse (c)   Zero (d) 900 Ans. b (9)

4. The angle of contact between glass and mercury is

(a)      0° (b)    30o (c)   90o                                                        (d)  135o Ans. d (6)

3. When the temperature is increased the angle of contact of a liquid

(a)  Increases (b)  Decreases (c)   Remains the same (d)  First increases and then decreases Ans. b (8)

2. The meniscus of mercury in the capillary tube is

(a)  Convex (b)  Concave (c)   Plane (d)  Uncertain Ans. a (4)

1. A liquid does not wet the sides of a solid, if the angle of contact is

(a)  Zero (b)  Obtuse (More than 90°) (c)   Acute (Less than 90°) (d)  90° Ans. b (9)

30. The excess pressure in a soap bubble is thrice that in other one. Then the ratio of their volume is

(a)  1 : 3 (b)  1 : 9 (c)   27 : 1 (d)  1 : 27 Ans. d (5)

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