HL Deep Dives — Rigid Bodies & Relativity

Solid sphere, no slip. Rotational KE is $\tfrac{2}{7}$ of the total.

Earth frame uses time dilation ($\tau = \gamma\tau_0$); muon frame uses length contraction ($L = L_0/\gamma$). Both predict the same survival fraction.

Use this whenever the non-relativistic shortcut gives $\beta > 0.3$ (or worse, $\beta > 1$).

Same in every frame. For photons ($m = 0$): $E = pc$.