Air is pushed carefully into a soap bubble of radius \(r\) to double its radius. If the surface tension of the soap solution is \(T,\) then work done in the process is:

A liquid does not wet the solid surface if the angle of contact is:
1. equal to $\mathrm{}$\(45^{\circ}\)
2. equal to \(60^{\circ}\)$\mathrm{}$
3. greater then \(90^{\circ}\)$\mathrm{}$
4. zero 

A soap bubble, having a radius of \(1~\text{mm}\), is blown from a detergent solution having a surface tension of \(2.5\times 10^{-2}~\text{N/m}\)$$. The pressure inside the bubble equals at a point \(Z_0\) below the free surface of the water in a container. Taking \(g = 10~\text{m/s}^{2}\)${\mathrm{}}^{}$, the density of water \(= 10^{3}~\text{kg/m}^3\)${\mathrm{}}^{}$, the value of \(Z_0\) is:
1. \(0.5~\text{cm}\)
2. \(100~\text{cm}\)
3. \(10~\text{cm}\)
4. \(1~\text{cm}\)

A rectangular film of liquid is extended from \((4~\text{cm} \times 2~\text{cm})\) to \((5~\text{cm} \times 4~\text{cm}).\) If the work done is \(3\times 10^{-4}\) J, the value of the surface tension of the liquid is:
1. \(0.250\) Nm^–1
2. \(0.125\) Nm^–1
3. \(0.2\) Nm^–1
4. \(8.0\) Nm^–1

A certain number of spherical drops of a liquid of radius \({r}\) coalesce to form a single drop of radius \({R}\) and volume \({V}\). If \({T}\) is the surface tension of the liquid, then: