Why does the free surface of a liquid tend to contract?

$A$ metal sheet $4 \ m$ on a side and of negligible thickness is attached to a balance and inserted into a container of fluid. The balance to which the metal sheet is attached reads $0.50 \ N$ and the contact angle is found to be $0^{\circ}$. $A$ small amount of oil is then spread over the metal sheet. The contact angle now becomes $180^{\circ}$ and the balance now reads $0.49 \ N$. The surface tension of the fluid is:

Small liquid drops assume a spherical shape because

Oil spreads over the surface of water whereas water does not spread over the surface of the oil,due to

$A$ metal wire of length $L$ and density $d$ floats horizontally on the free surface of water. What is the maximum radius of the wire such that it does not sink in water? [$T$ = surface tension of water, $g$ = gravitational acceleration]

$A$ liquid drop of density $\rho$ is floating half immersed in a liquid of surface tension $S$ and density $\frac{\rho}{2}$. If the surface tension $S$ of the liquid is numerically equal to $10$ times the acceleration due to gravity $g$,then the diameter of the drop is: