The surface of water in a water tank of cross-section area $750$ cm$^2$ on the top of a house is $h$ m above the tap level. The speed of water coming out through the tap of cross-section area $500$ mm$^2$ is $30$ cm/s. At that instant, $dh/dt$ is $y \times 10^{-3}$ m/s. The value of $y$ will be

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

Three liquids have same surface tension and have densities $\rho_1, \rho_2$ and $\rho_3$ $(\rho_1 > \rho_2 > \rho_3)$. In three identical capillaries rise of liquid is same. The corresponding angles of contact $\theta_1, \theta_2$ and $\theta_3$ are related as

The work done in splitting a water drop of radius 'R' into 64 droplets is (T is the surface tension of water)