$A$ horizontal pipe line carries water in a streamline flow. At a point along the tube where the cross-sectional area is $10^{-2} \ m^2$,the water velocity is $2 \ m/s$ and the pressure is $8000 \ Pa$. The pressure of water at another point where the cross-sectional area is $0.5 \times 10^{-2} \ m^2$ is ........ $Pa$.

$Assertion :$ The velocity of flow of a liquid is smaller when pressure is larger and vice-versa.
$Reason :$ According to Bernoulli's theorem,for the stream line flow of an ideal liquid,the total energy per unit mass remains constant.

Water flows in a horizontal tube (see figure). The pressure of water changes by $700 \; Nm^{-2}$ between $A$ and $B$ where the area of cross-section are $40 \; cm^{2}$ and $20 \; cm^{2},$ respectively. Find the rate of flow of water through the tube in $cm^{3} / s$. (Density of water $= 1000 \; kgm^{-3}$)

The velocity of kerosene oil in a horizontal pipe is $5 \ m/s$. If $g = 10 \ m/s^2$,then the velocity head of the oil will be ....... $m$.

Explain why the roof of a building flies off during a stormy wind.

Consider a completely full cylindrical water tank of height $1.6 \ m$ and cross-sectional area $0.5 \ m^2$. It has a small hole in its side at a height $90 \ cm$ from the bottom. Assume the cross-sectional area of the hole to be negligibly small as compared to that of the water tank. If a load of $50 \ kg$ is applied at the top surface of the water in the tank,then the velocity of the water coming out at the instant when the hole is opened is ......... $m/s$ $(g=10 \ m/s^2)$.