$A$ liquid flows steadily through a cylindrical pipe having a radius $2R$ at point $A$ and radius $R$ at point $B$ farther along the flow direction. If the velocity at point $B$ is $4v$, what will be the velocity at point $A$?

$A$ pipe having an internal diameter $D$ is connected to another pipe of the same size. Water flows into the second pipe through $n$ holes, each of diameter $d$. If the water in the first pipe has speed $v$, what is the speed of water leaving the second pipe?

Water flows through a horizontal pipe at a speed $V$. The internal diameter of the pipe is $d$. If the water is emerging from a nozzle at a speed $V_{1}$,then the diameter of the nozzle is

The surface of water in a water tank of cross-section area $750 \text{ cm}^2$ on the top of a house is $h \text{ m}$ above the tap level. The speed of water coming out through the tap of cross-section area $500 \text{ mm}^2$ is $30 \text{ cm/s}$. At that instant, $dh/dt$ is $y \times 10^{-3} \text{ m/s}$. The value of $y$ will be

Water flows through a horizontal pipe of varying cross-section at the rate of $\pi \times 10^{-1} \,m^3/s$. The velocity of water at a point where the radius of the pipe is $10 \,cm$ is $(\pi = 3.14)$. (in $\,m/s$)

Explain the concept of a tube of flow.