Question

A snap bubble is being blown on a tube of radius 1 cm. the surface tension of the soap solution is 0.05 N/m and the bubble makes an angle of ${60}^o$ with the tube as shown . The excess of pressure over the atmospheric pressure in the tube is:

• A. 5 Pa
• B. 1 Pa
• C. 10 Pa
• D. 20 Pa

Answer 1

The correct option is A 5 Pa

$\cos \theta =r/R=1/2$

$4\pi rT\cos \theta =\pi r^2△P$

$△P=\frac{4\pi rT\cos \theta }{\pi r^2}$

$△P=\frac{4\times 0.05}{0.01\times 2}$

$△P=5$Pa