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
T = 2π√(L/g) — simple pendulum, small angle.
How to verify the result
Square the period ratio when comparing lengths: T² is proportional to L when g is unchanged. Lower gravity increases period.
Domain and assumption boundary
Length and gravity must be positive. Large-angle, damping and distributed-mass effects are excluded. The calculator does not silently add drag, damping, deformation, varying fields, relativistic effects, measurement uncertainty, or geometry that the selected model does not contain.