Two soap bubbles of radii r1 and r2 equal to 4 cm and 5 cm respectively are touching each other over a common surface A B (shown in figure). Its radius will be

Question

Two soap bubbles of radii r1 and r2 equal to 4 cm and 5 cm respectively are touching each other over a common surface A B (shown in figure). Its radius will be (A) 4 cm (B) 4.5 cm (C) 5 cm (D) 20 cm

Tardigrade Admin · Accepted Answer

Excess pressure (4 S/r1)-(4 S/r2)=(4 S/r) or (1/r)=(1/r1)-(1/r2)=(1/4)-(1/5)=(1/20) or r=20 cm

Q. Two soap bubbles of radii $r_{1}$ and $r_{2}$ equal to $4 c m$ and $5 c m$ respectively are touching each other over a common surface $A B$ (shown in figure). Its radius will be

4 cm

4.5 cm

5 cm

20 cm

Excess pressure $\frac{4 S}{r _{1}} - \frac{4 S}{r _{2}} = \frac{4 S}{r}$
or $\frac{1}{r} = \frac{1}{r _{1}} - \frac{1}{r _{2}} = \frac{1}{4} - \frac{1}{5} = \frac{1}{20}$
or $r = 20 c m$

Q. Two soap bubbles of radii r1​ and r2​ equal to 4cm and 5cm respectively are touching each other over a common surface AB (shown in figure). Its radius will be