What mass should be suspended from the wire $CD$ to keep it in equilibrium?

What causes the free surface of a liquid to have minimum area?

Soap helps in cleaning clothes,because

$A$ square wire frame of each side $L$ is dipped in soap solution. On taking out, a membrane is formed. If the surface tension of the solution is $T$, the force acting on the frame will be (in $T L$)

$A$ wooden stick of length $2 \ m$ floats on water. The surface tension of water is $0.07 \ N/m$. If a soap solution with a surface tension of $0.06 \ N/m$ is applied to one side of the stick,what will be the net force acting on it in $N$?

$A$ drop of some liquid of volume $0.04 \ cm^{3}$ is placed on the surface of a glass slide. Then another glass slide is placed on it in such a way that the liquid forms a thin layer of area $20 \ cm^{2}$ between the surfaces of the two slides. To separate the slides a force of $16 \times 10^{5} \ dyne$ has to be applied normal to the surfaces. The surface tension of the liquid is (in $dyne \ cm^{-1}$):