The excess pressure inside a soap bubble of radius 2.5 cm is 48 dyne/cm ². The surface tension of soap in dyne /cm is (a) 25 (b) 30 (c) 35 (d) 40

Answer: (b). For a soap bubble (two surfaces) Δ P = 4T/R, so T = (Δ P · R)/(4). T = (48 × 2.5)/(4) = 30 dyne/cm So the answer is (b) 30.

The excess pressure inside a soap bubble of radius 2.5 cm is 48… | MHT CET 2026 (20 Apr, Shift 1)

Q2MHT CET 2026 · 20 APR · SHIFT 1Easy

Excess Pressure: Drops & Bubbles

The excess pressure inside a soap bubble of radius $2.5$ cm is $48$ dyne/cm ${}^{2}$ . The surface tension of soap in dyne /cm is

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Answer: (b)

For a soap bubble (two surfaces) $\Delta P = \frac{4T}{R}$ , so $T = \frac{\Delta P \cdot R}{4}$ .
$T = \frac{48 \times 2.5}{4} = 30$ dyne/cm
So the answer is (b) $30$ .

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