A water drop breaks into 64 identical droplets of each surface area $10^{-7} \mathrm{~m}^2$. If the surface tension of water is $0.07 \mathrm{Nm}^{-1}$, the increase in the surface energy in the process is

A cylindrical vessel, open at the top, contains 15 litres of water. Water drains out through a small opening at the bottom. 5 litre of water comes out in time $t_1$, the next 5 litre in further time $t_2$, and the last 5 litre in further time $t_3$, Then

A cylinder of mass $m$ and material density $\rho$ hanging from a string is lowered into a vessel of cross-sectional area $A$ containing a liquid of density $\sigma(<\rho)$ until it is fully immersed. The increase in pressure at the bottom of the vessel is

The angle of contact is $120^{\circ}$ when a cylindrical rod is vertically placed in a liquid. If the same rod is placed horizontally in the liquid, then the angle of contact is