 Endpoint collision of two freely rotating equal rods

Each massless rod has endpoint masses $m$ at distance $\ell$ from its centre, hence total mass $2m$ and moment of inertia $2m{\ell }^2$. In a symmetric opposite-end collision with centres approaching at speed $V$, a horizontal impulse $J$ changes each centre speed by $J/(2m)$ and each contact-point speed by $J/m$. The coefficient of restitution gives $2J/m-2V=2eV$. Both rods rotate in the same sense for the staggered vertical configuration; their centre speeds after impact are $V(3-e)/4$.

// Target: electromagnetism.bigb