$A$ sniper fires a rifle bullet into a gasoline tank,making a hole $53.0 \ m$ below the surface of the gasoline. The tank was sealed at $3.10 \ atm$. The stored gasoline has a density of $660 \ kg \ m^{-3}$. The velocity with which gasoline begins to shoot out of the hole is ........ $m \ s^{-1}$.

$A$ tank of height $15 \ m$ and cross-section area $10 \ m^2$ is filled with water. There is a small hole of cross-section area $a$ which is much smaller than the container, located at a height of $12 \ m$ from the base of the container. How much force should be applied with a piston at the top level, so that the water coming out of the hole hits the ground at a distance of $16 \ m$ (in $kN$)? (Take, density of water $\rho = 1000 \ kg \ m^{-3}$ and $g = 10 \ m/s^2$)

Why do two rowing boats moving parallel to each other come closer (attract) to each other?

The flow speeds of air on the lower and upper surfaces of the wing of an aeroplane are $v$ and $2v$ respectively. The density of air is $\rho$ and the surface area of the wing is $A$. The dynamic lift on the wing is:

Water is flowing through a horizontal tube having cross-sectional areas of its two ends as $A$ and $A'$ such that the ratio $A/A'$ is $5$. If the pressure difference of water between the two ends is $3 \times 10^5 \, N \, m^{-2}$,the velocity of water with which it enters the tube will be ......... $m \, s^{-1}$ (neglect gravity effects).

State Bernoulli's principle in words.