Question

Water is slowly coming out from a vertical pipe. As the water descends after coming out, its area of cross section reduces. Explain this on the basis of the equation of continuity.

Answer 1

Let a be the area of cross section and v be the velocity of water.
According to the equation of continuity,
av = Constant
or, $v\alpha \frac{1}{a}$
It means the larger the area of cross section, the smaller will be the velocity of liquid and vice versa.
Thus, as the water comes out of the vertical pipe, its velocity increases and area of cross section decreases.