Rotational equipartition in a rough-ball gas
= Rotational equipartition in a rough-ball gas
Rough elastic collisions can exchange rotational and translational <kinetic energy>. For three-dimensional rigid balls with all three rotations thermalized, these six quadratic terms contribute $3k_BT$ per particle. A uniform gravitational height distribution adds $k_BT$, giving total mechanical mean energy $4k_BT$.