Question

The pressure of air in a soap bubble of 0.7cm diameter is 8 mm of water above the pressure outside. The surface tension of the soap solution is

• A. 100 dyne / cm
• B.
• C. 137 dyne / cm
• D. 150 dyne / cm

Answer 1

Answer: (B)

Answer 2

$\Delta P = \frac { 4 T } { r } = h d g \Rightarrow T = \frac { r h d g } { 4 }$ $= \frac { 0.35 \times 0.8 \times 1 \times 10 ^ { 3 } } { 4 }$