$A$ liquid is flowing in a horizontal pipe of non-uniform cross-section. Which of the following quantities may remain unchanged with respect to time?

$A$ 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 $(g = 10\ m/s^2)$ ....... $m/s$

$A$ scent sprayer is based on

Consider a cylindrical tank of radius $1\,m$ filled with water. The top surface of the water is at $15\,m$ from the bottom of the cylinder. There is a hole on the wall of the cylinder at a height of $5\,m$ from the bottom. $A$ force of $5 \times 10^{5}\,N$ is applied on the top surface of the water using a piston. Calculate the speed of efflux from the hole. (Given: atmospheric pressure $P_{A} = 1.01 \times 10^{5}\,Pa$,density of water $\rho_{w} = 1000\,kg/m^{3}$,and gravitational acceleration $g = 10\,m/s^{2}$) (in $,m/s$)

Air is streaming past a horizontal airplane wing such that its speed is $120 \ m/s$ over the upper surface and $90 \ m/s$ at the lower surface. If the density of air is $1.3 \ kg/m^3$ and the wing is $10 \ m$ long and has an average width of $2 \ m$,then the difference of the pressure on the two sides of the wing is ....... $Pascal$.

$A$ steady flow of a liquid of density $\rho$ is shown in the figure. At point $1$,the area of cross-section is $2A$ and the speed of flow of liquid is $\sqrt{2} \ m \ s^{-1}$. At point $2$,the area of cross-section is $A$. Between the points $1$ and $2$,the pressure difference is $100 \ N \ m^{-2}$ and the height difference is $10 \ cm$. The value of $\rho$ is (Acceleration due to gravity $= 10 \ m \ s^{-2}$) (in $kg \ m^{-3}$)