Q115 / 150 · MHT CET 2026 (20 April Shift 1) · Physics
The excess pressure inside a soap bubble of radius $2.5$ cm is $48$ dyne/cm$^2$. The surface tension of soap solution in dyne /cm is
- A$25$
- Correct answerB$30$
- C$35$
- D$40$
Solution
The excess pressure inside a soap bubble is given by $\Delta P = \dfrac{4T}{R}$
where $T$ is the surface tension and $R$ is the radius of the bubble.
Given, $\Delta P = 48$ dyne/cm$^2$ and $R = 2.5$ cm.
Substituting the values, we get:
$48 = \dfrac{4T}{2.5}$
$T = \dfrac{48 \times 2.5}{4}$
$T = 12 \times 2.5 = 30$ dyne/cm
Answer: $30$
where $T$ is the surface tension and $R$ is the radius of the bubble.
Given, $\Delta P = 48$ dyne/cm$^2$ and $R = 2.5$ cm.
Substituting the values, we get:
$48 = \dfrac{4T}{2.5}$
$T = \dfrac{48 \times 2.5}{4}$
$T = 12 \times 2.5 = 30$ dyne/cm
Answer: $30$
Hence, the correct answer is option: 'B'.