Question

A soap bubble of radius r is blown up to form a bubble of radius 2r under isothermal conditions if the T is the surface tension of soap solution the energy spent in the slowing is. 

(A) 3πTr² 

(B) 6πTr² 

(C) 12πTr² 

(D) 24πTr²

Answer 1

Correct option: (D) 24πTr²

Explanation:

In case of soap bubble.

W = 8πT(R₂² – R₁²)

Given : R₁ = r ,        R₂ = 2r

∴ W = 8πT(4r² – r²)

W = 24πTr² 

i.e. energy spent is 24πTr²