Question

The work done in blowing a soap bubble of radius $R$ is $W_1$ and that to a radius $3R$ is $W_2$. the ratio of work done is

• A. $1:3$
  
• B. $3:1$
  
• C. $1:9$
  
• D. $9:1$
  

Answer 1

The correct option is C $1:9$

Since work done in blowing a bubble = $T△A$

given $r_1=R\&r_2=3R$

So, $\frac{w_1}{w_2}=\frac{△A_1}{△A_2}=\frac{\pi r_1^2}{\pi r_2^2}={\left(\frac{r_1}{r_2}\right)}^2={\left(\frac{R}{3R}\right)}^2=\frac{1}{9}$