Keep in mind that the section property Q relates to
longitudinal resultant forces from the bending stress distribution
that act on a specific area of the cross section. Since the bending stress
distribution is linearly distributed about the centroidal axis, Q
must also be calculated with reference to the centroidal axis.
For this cross section, board (3) must be attached to the other two boards. To find Q, we compute the moment of area (3) about the z centroidal axis.
