$(20)$ A concrete form shown to the right is filled with wet

concrete, which has a specific gravity of $2\mathrm{.}5.$ Section

AB of the form is triangular, with a base that is $3$ ft

wide.

FOREMULa MET HOD

Determine the resultant force of the concrete on

the side of the form.

$F_R$

Sketch $AB$ with the resultant force acting in the

correct location. $($Do not simply draw it on the

original diagram.$)$

SKETCH

Determine the moment of the resultant force

about the base of the triangle $($point $B).$