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

An aircraft of mass $3 \times 10^5 \ kg$ with total wing area $400 \ m^2$ is in a level flight at a speed of $540 \ km \ h^{-1}$. The density of air at its height is $1.2 \ kg \ m^{-3}$. The fractional increase in the speed of the air on the upper surface of its wings relative to the lower surface is . . . . . . $\left(g=10 \ ms^{-2}\right)$

Water flows through the tube shown. The cross-sectional areas of the wide and narrow parts are $5 \text{ cm}^2$ and $2 \text{ cm}^2$,respectively. The rate of flow is $500 \text{ cm}^3/\text{s}$. Find the difference in the mercury level of the $U$-tube in $\text{cm}$.

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

Different heads are in Column - $I$ and their formulas are given in Column - $II$. Match them appropriately.

Column - $I$	Column - $II$
$(a)$ Velocity head	$(i)$ $\frac{P}{\rho g}$
$(b)$ Pressure head	$(ii)$ $h$
$(c)$ Potential head	$(iii)$ $\frac{v^2}{2g}$

$A$ 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 . . . . . . $\text{Pa}$.