Question

what is the work done in blowing a soap bubble of radius r and surface tension s?

Answer 1

We know that a bubble has two surfaces in contact with air, so the total surface area of the bubble will be
=2×(4πR2)=8πR2Now, work done=Surface tension × Increase in surface area=T×(8πR2−0)=8πR2T

Answer 2

Answer:

8πr²T

Explanation:

Radius of soap bubble = r (Given)

Surface tension of soap bubble = s (Given)

Work = Force × Displacement OR

Work = Surface tension × Change in the surface area

The bubble always has two surfaces- the outer surface and the inner surface, thus the total surface area of bubble will be -

= 2 × 4πr²

= 8πr²

Since work done = Surface Tension × Increase in the surface area

= T × ( 8πr² - 0 )

= 8πr²T

Therefore, the work done  in blowing a soap bubble of radius r and surface tension is 8πr²T.