Exercise $6-$ A long vertical wall separates seawater from fresh water. If the seawater stands at a depth of $7$ m $,$ what depth of freshwater is required to give a zero resultant force on the wall. When the resultant force is zero, will the moment due to the fluid forces be zero?

$($a$)$ What is the depth of freshwater? $($ANSW $-7\mathrm{.}11$ m $)$

$($b$)$ What is the location of force $F_{\text{s}\text{e}\text{a}\text{w}\text{s}\text{e}\text{r}\text{e}\text{r}}?($ANSW $-4\mathrm{.}67$ m $)$

$($c$)$ What is the location of force $F_{\text{t}\text{r}\text{e}\text{s}\text{t}\text{w}\text{a}\text{t}\text{e}\text{r}}?($ANSW $-4\mathrm{.}74$ m $)$

$($d$)$ Are the forces colinear?