Question

The surface tension in a soap bubble of 50 mm diameter with its inside pressure being 2.5 N/$m^2$ above the atmospheric pressure is

• A. 0.0125 N/m
• B. 0.0156 N/m
• C. 0.2 N/m
• D. 0.0312 N/m

Answer 1

The correct option is B 0.0156 N/m

$\rho \times \frac{\pi d^2}{4}=\sigma \times 2\left(2\pi r\right)=\sigma \times 2\pi d\sigma =\frac{pd}{8}=\frac{2.5\times 0.05}{8}=0.0156N/m$