🪢 Rubber Band (2D): Gent Stress-Strain Curve, Mass Bounce and Gough-Joule Heating

Canvas rubber-band lab: a Gent hyperelastic loop with a hanging mass or a tensile testing machine, nonlinear stress-strain curve, strain stiffening, the Gough-Joule heating of a stretched band, energy and bounce-frequency graphs, with numerical checks.