for a rectangular channel width $8$m$,$ discharge $15$m$^3/$s depth of flow $1\mathrm{.}5$m$.$

E$=$h$+$q$^2/2$gh$^2$

q$=$Q$/$w $=1\mathrm{.}875$

E$=1\mathrm{.}580$

derive an expression for critical depth in terms of q and g$.$ Specific energy E is minimum at critical depth by differentiating dE$/$dh$=0$

Then, find Critical depth $($hc$),$ Critical velocity $($Vc$)$ and value of minimum specific eneryg.