Question

The work done in blowing a soap bubble slowly from a radius of 5 cm to a radius of 10 cm is.................... Joule (given the surface tension of water is $3.5\times$ 10${}^{-2}$ N m${}^{-1}$):

• A. 6.6 $\times$ 10${}^{-3}$
• B. 2.2 $\times$ 10${}^{-3}$
• C. 4.4 $\times$ 10${}^{-3}$
• D. 8.8 $\times$ 10${}^{-3}$

Answer 1

The correct option is A 6.6 $\times$ 10${}^{-3}$

Work done in blowing a soap bubble $W=2T(A_2-A_1)$

now $r_1=0.05m,r_2=0.1m$

So $W=2T(4\pi r_2^2-4\pi r_1^2)=8\pi T({0.1}^2-{0.05}^2)=6.6\times {10}^{-3}J$