Structural Engineering & Statics
where the load goes
Generator

The moment-arm generator

Rendered here at the parameters it defaults to, with every essay that calls it — which is the same list as the blast radius of changing it.
The moment is the force times the distanceOne force applied at five distances from a pivot, with the moment it produces drawn as a bar. The force never changes; only the arm does, and the moment follows it exactly.pivotthe same force of 20, moved along the levermoment about the pivot120 × 1 = 20220 × 2 = 40320 × 3 = 60420 × 4 = 80520 × 5 = 100

2 essays call moment-arm. The drawing above is what it returns with no arguments at all; every call below passes it something, because a placement that passes nothing draws whichever member of the family the generator happens to default to rather than the one its essay argues about.

Where it is called

Changing this generator changes every one of these figures.

1289.510.5ΣM about one support gives the other reaction; ΣF then gives the first Equilibrium

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.

 1289.510.5ΣM = 0about AΣM = 0about BΣM = 0about CΣM about one support gives the other reaction; ΣF then gives the first Equilibrium

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 whole library