Water is flowing through a tube of radius r with a speed v. If this tube is joined to another tube of radius <img alt="\mathrm{r / 2}" src="https://entrancecorner.oncodecogs.com/gif.latex?%5Cm
Water is flowing through a tube of radius r with a speed v. If this tube is joined to another tube of radius , what is the speed of water in the second tube?