Question

Calculate the work done in blowing a soap bubble of radius 4 cm. The surface tension of the soap solution is 25 × 10^-3 N/m.

Answer 1

Data : r = 4 cm = 4 × 10^-2 m, T = 25 × 10^-3 N/m

Initial surface area of soap bubble = 0 

Final surface area of soap bubble = 2 × 4πr² 

Increase in surface area = 2 × 4πr ² 

The work done = surface tension x increase in surface area 

= T × 2 × 4πr²

= 25 × 10^-3 × 2 × 4 × 3.142 × (4 × 10^-2)²

= 1.005 × 10^-3 J