Concept
Independent equations
2 essays name this object, across one field. What follows is each of them, and the objects they name alongside it.
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.
The count that does not see it
A frame can have exactly as many unknowns as equations and fold up anyway. The count asks whether there are enough equations; it never asks whether they are different from one another.
Named alongside it
The objects these essays reach for when they reach for this one.
BracingCritical formDeterminacyEquilibrium matrixForce equilibriumFree body diagramLine of actionMechanismMoment centreMoment equilibriumRank deficiencyRigid body