What is a tube of flow?

Two water pipes $P$ and $Q$ having diameters $2 \times 10^{-2} \ m$ and $4 \times 10^{-2} \ m$,respectively,are joined in series with the main supply line of water. The velocity of water flowing in pipe $P$ is

In a streamlined flow,the velocity of a fluid at a given point

Give an example of steady flow.

Can two streamlines cross each other? Why?

Water coming out of the mouth of a tap and falling vertically in streamline flow forms a tapering column,i.e.,the area of cross-section of the liquid column decreases as it moves down. Which of the following is the most accurate explanation for this?