Home | | Physics 11th std | Solved Example Problems for Surface tension

# Solved Example Problems for Surface tension

Physics : Properties of Matter - Solved Example Problems for Surface tension

## EXAMPLE 7.10

Let 2 .4├Ś10ŌłÆ4 J of work is done to increase the area of a film of soap bubble from 50 cm2 to 100 cm2. Calculate the value of surface tension of soap solution.

Solution:

A soap bubble has two free surfaces, therefore increase in surface area ŌłåA = A2ŌłÆA1 = 2(100-50) ├Ś 10-4m2 = 100 ├Ś 10-4m2.

Since, work done W = T ├Ś╬öA ŌćÆT = ## EXAMPLE 7.11

If excess pressure is balanced by a column of oil (with specific gravity 0.8) 4ŌĆåmm high, where R = 2.0ŌĆåcm, find the surface tension of the soap bubble.

### Solution

The excess of pressure inside the soap bubble is = 15.68 ├Ś10ŌłÆ 2 N mŌłÆ1

### EXAMPLE 7.12

Water rises in a capillary tube to a height of 2.0cm. How much will the water rise through another capillary tube whose radius is one-third of the first tube?

### Solution

From equation (7.34), we have

ŌłØ 1/r ŌćÆhr =constant

Consider two capillary tubes with radius r1 and r2 which on placing in a liquid, capillary rises to height h1 and h2, respectively. Then, ### EXAMPLE 7.13

Mercury has an angle of contact equal to 140┬░ with soda lime glass. A narrow tube of radius 2ŌĆåmm, made of this glass is dipped in a trough containing mercury. By what amount does the mercury dip down in the tube relative to the liquid surface outside?. Surface tension of mercury T=0.456 NŌĆåm-1; Density of mercury Žü = 13.6 ├Ś 103 kg m-3

### Solution

Capillary descent, where, negative sign indicates that there is fall of mercury (mercury is depressed) in glass tube.

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail
11th Physics : UNIT 7 : Properties of Matter : Solved Example Problems for Surface tension |