Water flowing through an $8-cm-$diameter pipe enters a porous section, as in the figure given below, which allows a uniform

radial velocity $v_W$ through the wall surfaces for a distance of $1\mathrm{.}2$ m $.$ The entrance average velocity $V_1$ is $40\frac{m}{s}.$

Calculate the exit velocity $V_2$ if $v_W=15c\frac{m}{s}$ out of the pipe walls.