Revision Chapter (3)
1. Show that the excess pressure inside a soap bubble of radius \( r \) over the atmospheric pressure outside it is equal to \( \frac{4 T}{r} \), where \( T \) is the surface tension of the soap solution.
2. Define the angle of contact.
- Show how the existence of an acute angle of contact and of a pressure difference due to curvature accounts for the rise of liquid in a capillary tube.
3. Derive the relation between the surface tension of a liquid and its height in a capillary tube.