Question

A rectangular film of liquid is extended from (4 cm 2 cm) to (5 cm 4 cm). If the work done is 3 104 j, the value of the surface tension of the liquid is

Answer 1

Answer:

Increase in surface area = (20 cm2-8 cm2)×2

= 12×2 cm2

= 24 cm2 (film has two surfaces)

So work done = T Δ S = T × 24 × 10-4 = 3×10-4

so T = 3/24 N/m = 1/8 Nm-1 = 0.125 N/m