If a section of a soap bubble of radius $r$ by a plane through its centre is considered,the force on the half due to surface tension is

$216$ small identical liquid drops,each of surface area $A$,coalesce to form a bigger drop. If the surface tension of the liquid is $T$,what is the energy released in the process (in $AT$)?

Two small drops of mercury,each of radius $R$,coalesce to form a single large drop. The ratio of the total surface energies before and after the change is:

Small drops of liquid of the same radius coalesce to form a big drop. The ratio of the total surface energies after and before the change is:

The excess pressure inside a soap bubble is three times that of another soap bubble. The ratio of their volumes is:

In air,a charged soap bubble of radius $R$ breaks into $27$ small soap bubbles of equal radius $r$. Then,the ratio of mechanical force acting per unit area of the big soap bubble to that of a small soap bubble is