Three liquids of equal masses are taken in three identical cubical vessels $A,B$ and $C$. Their densities are ${\rho }_{\mathrm{A}},{\rho }_{\mathrm{B}}$ and ${\rho }_{\mathrm{C}}$ respectively but ${\rho }_{\mathrm{A}}<{\rho }_{\mathrm{B}}<{\rho }_{\mathrm{C}}$. The force exerted by the liquid on the base of the cubical vessel is

Two liquids of densities ${\rho }_1$ and ${\rho }_2\left({\rho }_2=2{\rho }_1\right)$ are filled up behind a square wall of side $10 \mathrm{m}$ as shown in figure. Each liquid has a height of $5 \mathrm{m}$. The ratio of the forces due to these liquids exerted on upper part $MN$ to that at the lower part $NO$ is (assume that the liquids are not mixing)

Water flows in a horizontal tube (see figure). The pressure of water changes by $700 \mathrm{N} {\mathrm{m}}^{-2}$ between $A$ and $B$, where the area of cross-section are $40 {\mathrm{cm}}^2$ and $20 {\mathrm{cm}}^2$, respectively. Find the rate of flow of water through the tube (Take, density of water $=1000 \mathrm{kg} {\mathrm{m}}^{-3}$).