2D box: particles with fixed total kinetic energy
Phase space (q, p) for particle 1: energy circle
Energy distribution & Ω(E) curve
Each particle bounces elastically in the box. Total kinetic energy is conserved (microcanonical constraint).
The phase-space panel shows the accessible region H ≤ E for one particle. The right panel plots Ω(E) ∝ E for a 1D particle.