$A$ scent sprayer is based on

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 ....... $m$.

Water flows steadily through a horizontal pipe of variable cross-section. If the pressure of water is $P$ at a point where flow speed is $v$,the pressure at another point where the flow speed is $2v$,is (Take density of water as $\rho$)

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

$A$ large cylindrical tank of cross-sectional area $1\ m^2$ is filled with water. It has a small hole at a height of $1\ m$ from the bottom. $A$ movable piston of mass $5\ kg$ is fitted on the top of the tank such that it can slide in the tank freely without friction. $A$ load of $45\ kg$ is applied on the top of the water by the piston,as shown in the figure. The value of $v$ when the piston is $7\ m$ above the bottom is $(g = 10\ m/s^2)$ ....... $m/s$

In the case of a fluid,Bernoulli's theorem expresses the application of the principle of conservation of :