At what speed will the velocity head of a stream of water be equal to $40 \ cm$ of $Hg$ (in $cm/sec$)?

Water is flowing steadily through a horizontal tube of non-uniform cross-section. If the pressure of water is $4 \times 10^4 \ N/m^2$ at a point where the cross-section is $0.02 \ m^2$ and the velocity of flow is $2 \ m/s$,what is the pressure at a point where the cross-section reduces to $0.01 \ m^2$?

$A$ horizontal pipe of non-uniform cross-section allows water to flow through it with a velocity $1 \ m/s$ when the pressure is $50 \ kPa$ at a point. If the velocity of flow has to be $2 \ m/s$ at some other point, the pressure at that point should be: (in $kPa$)

$A$ fully loaded Boeing aircraft has a mass of $5.4 \times 10^5 \, kg$. Its total wing area is $500 \, m^2$. It is in level flight with a speed of $1080 \, km/h$. If the density of air $\rho$ is $1.2 \, kg/m^3$,the fractional increase in the speed of the air on the upper surface of the wing relative to the lower surface in percentage will be $(g = 10 \, m/s^2)$.

$A$ closed pipe containing liquid showed a pressure $P_1$ by gauge. When the valve was opened, the pressure was reduced to $P_2$. The speed of water flowing out of the pipe is ($\rho$ = density of water).

Air streams horizontally past an airplane. The speed over the top surface is $60 \, m/s$ and that under the bottom surface is $45 \, m/s$. The density of air is $1.293 \, kg/m^3$. The difference in pressure is ....... $N/m^2$.