Concept
Force equilibrium
2 essays name this object, across one field. What follows is each of them, and the objects they name alongside it.
Also named here as rigid body — the same set of essays touches all of them, so they are one junction rather than several.
Everything adds to nothing, and that is the whole of statics
A structure that stays put obeys two statements — the forces on it sum to zero, and so do the moments. Every number in the subject comes out of those two sentences.
The equation that is not new, and the three that are
A plane free body yields exactly three independent equations. Most attempts at a fourth are one of the first three wearing different clothes — and on a beam under vertical load, one of the three is already saying nothing.
Named alongside it
The objects these essays reach for when they reach for this one.
Free body diagramMoment equilibriumRigid bodyDeterminacyIdealisationIndependent equationsLine of actionMoment centreReactions