Water flows in a horizontal tube as shown in the figure. The pressure of water changes by $600\, N/m^2$ between $A$ and $B$ where the cross-sectional areas are $30\, cm^2$ and $15\, cm^2$ respectively. Find the rate of flow of water through the tube.

Air of density $1.2 \, kg \, m^{-3}$ is blowing across the horizontal wings of an aeroplane in such a way that its speeds above and below the wings are $150 \, m \, s^{-1}$ and $100 \, m \, s^{-1}$,respectively. The pressure difference between the upper and lower sides of the wings is ........ $N \, m^{-2}$.

Why does a flag (or ensign) flutter when there is strong wind? Explain.

The reading of a pressure gauge connected to a closed tap is $3.5 \times 10^5 \, N/m^2$. When the tap is opened,the reading of the pressure gauge falls to $3.0 \times 10^5 \, N/m^2$. The velocity of water is ........ $m/s$.

$A$ 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 ........ $m \ s^{-1}$.

Consider a water tank as shown in the figure. Its cross-sectional area is $0.4\, m^{2}$. The tank has an opening $B$ near the bottom whose cross-sectional area is $1\, cm^{2}$. $A$ load of $24\, kg$ is applied on the water at the top. When the height of the water level is $40\, cm$ above the bottom,the velocity of water coming out of the opening $B$ is $v\, ms^{-1}$. The value of $v$,to the nearest integer,is ......$m/s$. [Take value of $g$ to be $10\, ms^{-2}$]