JEE PYQ: Mechanical Properties Of Fluids Question 3
Question 3 - 2021 (17 Mar 2021 Shift 1)
When two soap bubbles of radii $a$ and $b$ ($b > a$) coalesce, the radius of curvature of common surface is:
(1) $\frac{ab}{b-a}$
(2) $\frac{a+b}{ab}$
(3) $\frac{b-a}{ab}$
(4) $\frac{ab}{a+b}$
Show Answer
Answer: (1) $\frac{ab}{b-a}$
Solution
Excess pressure at common surface is given by $P_{ex} = 4T\left(\frac{1}{a} - \frac{1}{b}\right) = \frac{4T}{r}$ $\therefore \frac{1}{r} = \frac{1}{a} - \frac{1}{b}$ $r = \frac{ab}{b - a}$
BETA
