Why does fluid flow faster in a narrow tube?

$A$ 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 $v$,the speed of water leaving the second pipe is

$A$ gardening pipe having an internal radius '$R$' is connected to a water sprinkler having '$n$' holes each of radius '$r$'. The water in the pipe has a speed '$v$'. The speed of water leaving the sprinkler is

The cylindrical tube of a spray pump has a cross-section of $8 \,cm^{2}$, one end of which has $40$ fine holes each of area $10^{-8} \,m^{2}$. If the liquid flows inside the tube with a speed of $0.15 \,m \,min^{-1}$, the speed with which the liquid is ejected through the holes is (in $\,ms^{-1}$)

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

The Bhagirathi and the Alaknanda merge at Deoprayag to form the Ganga. The speeds of the Bhagirathi and the Alaknanda are in the ratio $1: 1.5$. The cross-sectional areas of the Bhagirathi,the Alaknanda,and the Ganga are in the ratio $1: 2: 3$. Assuming streamline flow,the ratio of the speed of the Ganga to that of the Alaknanda is