State the model before trusting the number
Classical formulas are only as good as their assumptions and units. Air resistance, damping, deformation, non-constant forces and measurement uncertainty are not silently invented when the selected model does not include them.
Governing physics model
r̄ = Σmᵢrᵢ / Σmᵢ — 2D point-mass model.
How to verify the result
The center should stay inside the convex span of positive point masses; duplicating every mass by the same factor must not move it.
Domain and assumption boundary
Point-mass coordinates with positive masses and one consistent coordinate unit. The calculator does not silently add drag, damping, deformation, varying fields, relativistic effects, measurement uncertainty, or geometry that the selected model does not contain.