# Section modulus and radius of gyration
# Scope: Concentric circular tube; bending and torsion properties.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

outer = 30 mm
inner = 25 mm

area := pi*(outer^2-inner^2)/4 [mm^2]
inertia := pi*(outer^4-inner^4)/64 [mm^4]
polar := 2*inertia [mm^4]

check positive wall: outer > inner

scenario alternative: outer = 24 mm