My Notes
The radius of a soap bubble is increased from R to 2 R. Work done in this process (T = surface tension) is:
| 1. | 24 πR2T | 2. | 48 πR2T |
| 3. | 12 πR2T | 4. | 36 πR2T |
A certain number of spherical drops of a liquid of radius r coalesce to form a single drop of radius R and volume V. If T is the surface tension of the liquid, then:\(\text { Energy }=4 V T\left(\frac{1}{r}-\frac{1}{R}\right) \text { is released } \)
| 1. | Energy = \(4 V T\left(\frac{1}{r}-\frac{1}{R}\right)\) is released | 2. | Energy =\(3 V T\left(\frac{1}{r}+\frac{1}{R}\right)\) is released |
| 3. | Energy =\(3 V T\left(\frac{1}{r}-\frac{1}{R}\right)\) is released | 4. | Energy is neither released nor absorbed |
If a glass rod is dipped in mercury and withdrawn out, the mercury does not wet the rod because
(1) Angle of contact is acute
(2) Cohesion force is more
(3) Adhesion force is more
(4) The density of mercury is more
Mercury does not wet glass, wood or iron because
(1) Cohesive force is less than the adhesive force
(2) Cohesive force is greater than the adhesive force
(3) The angle of contact is less than 90o
(4) Cohesive force is equal to the adhesive force
When a drop of water is dropped on oil surface, then
(1) It will mix up with oil
(2) It spreads in the form of a film
(3) It will deform
(4) It remains spherical
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