Question

The diameter if a soap bubble is 5cm.The excess pressure inside the bubble is 2bar.Find the surface tension of the surface film of the bubble.

Answer 1

$\mathtt{\huge\fbox{Solution :}}$

Given,

• Diameter of soap bubble = 5 cm

So, radius of soap bubble = 2.5 cm = 0.025 m

The excess pressure inside the bubble = 2 bar

We know that, the excess pressure inside the bubble is given by

$\large{\mathtt{ \underline{\fbox{p_{i} -p _{o} = \frac{2t}{r} }}}}$

Where,

• (Pi - Po) is excess pressure inside the soap bubble
• t is the surface tension
• r is the radius of soap bubble

Substitute the known values , we get

$\sf \mapsto2 = \frac{2t}{0.025} \\ \\\sf \mapsto t = 0.025 \: newton \: per \: meter$

Hence, the surface tension is 0.025 newton/meter