Question 25, 2019 WACE Exam

This question talked about a “hoist truss”, rather than a Warren Truss, this was in 2019, the difference seemed to be that the triangles arem’t equilateral.
maybe Warren Truss ≠ Equilateral triangle? or MoS ≠ Warren Truss only?

Heres the Free-body I’ll use.
Already solved from earlier part of the question; $F_{BC}=9kN$ and I’m looking for $F_{BE}$.

Moment Arm

This is the one used in the marking key, it’s the most complex imo, but the syllabus implies it’s the government mandated (literally) way to do it.
Uses Moment Arms & Lines of Action, requires $F_{BC}$ to attempt it, and is worth double the marks.

Vertical Equilibrium

This is probably the easiest way, you don’t even need to know any other members in the truss, you can just go straight for $\Sigma F_Y$ since $F_{BC}$ is the only member with a vertical component that isn’t one of the all-vertical external forces.

The Vertical Component

Hoenstly this way is just kinda the worst all-round, it’s easier than Moment Arms, but harder than vertical equilibrium, it requires $F_{BC}$ which vertical equil. doesn’t.
Theres a half-decent chance it’s just straight-up wrong, this was my initial intuition on how to do method of sections before I wen’t back through Moment Arms / Lines of Actions, it does get the same answer though,

Reverse-engineering 2019 Marking Key

This was very satisfying / ==rewarding==