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

Is Bernoulli's equation unsteady? Explain.

$A$ liquid of density $600 \text{ kg/m}^3$ is flowing steadily in a tube of varying cross-section. The cross-section at a point $A$ is $1.0 \text{ cm}^2$ and that at $B$ is $20 \text{ mm}^2$. Both the points $A$ and $B$ are in the same horizontal plane,and the speed of the liquid at $A$ is $10 \text{ cm/s}$. The difference in pressures at $A$ and $B$ points is . . . . . . $\text{Pa}$.

In a test experiment on a model aeroplane in a wind tunnel,the flow speeds on the upper and lower surfaces of the wing are $70 \; m s^{-1}$ and $63 \; m s^{-1}$ respectively. What is the lift on the wing if its area is $2.5 \; m^{2}$? Take the density of air to be $1.3 \; kg m^{-3}$.

The velocity of kerosene in a horizontal pipe is $5 \ m/s$. What is the velocity head in $m$? (Take $g = 10 \ m/s^2$)

If the velocity of flow is $4 \, m/s$,then the velocity head is ......... $m$.