MCQ
The pressure of air in a soap bubble of $0.7\,cm$ diameter is $8\, mm$ of water above the pressure outside. The surface tension of the soap solution is ........ $dyne/cm$
- A$100$
- ✓$68.66$
- C$137$
- D$150$
✓
Answer
Correct option: B.
$68.66$
b
(b) $\Delta P = \frac{{4T}}{r} = hdg \Rightarrow T = \frac{{rhdg}}{4}$ $ = \frac{{0.35 \times 0.8 \times 1 \times {{10}^3}}}{4}$
(b) $\Delta P = \frac{{4T}}{r} = hdg \Rightarrow T = \frac{{rhdg}}{4}$ $ = \frac{{0.35 \times 0.8 \times 1 \times {{10}^3}}}{4}$
$ = 70\;dyne/cm$$ \equiv 68.66\;dyne/cm$
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