Water flows in a horizontal pipe whose one end is closed with a valve. The reading of the pressure gauge attached to the pipe is $P_1$. The reading of the pressure gauge falls to $P_2$ when the valve is opened. The speed of water flowing in the pipe is proportional to

$A$ wind with speed $50 \,m/s$ blows parallel to the roof of a house. The area of the roof is $300 \,m^2$. Assume that the pressure inside the house is atmospheric pressure. The density of air is $1.2 \,kg/m^3$. The magnitude of the force exerted by the wind on the roof will be:

The working of an atomizer depends upon:

$A$ horizontal pipe carries water in a streamlined flow. At a point along the pipe,where the cross-sectional area is $10 \text{ cm}^2$,the velocity of water is $1 \text{ ms}^{-1}$ and the pressure is $2000 \text{ Pa}$. What is the pressure of water at another point where the cross-sectional area is $5 \text{ cm}^2$ (in $Pa$)? [Density of water $= 1000 \text{ kgm}^{-3}$]

$A$ steady flow of water passes along a horizontal tube from a wide section $X$ to the narrower section $Y$,see figure. Manometers are placed at $P$ and $Q$ at the sections. Which of the statements $A, B, C, D$ is most correct?

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	$(iii)$ $\frac{v^2}{2g}$