 Virial theorem

For a confined Newtonian gravitational system, $\dot{G}=2T+V$ for $G=\sum p_i\cdot r_i$, hence $2⟨T⟩=-⟨V⟩$.

The virial theorem is a powerful result in classical mechanics and astrophysics, particularly useful for systems of particles bound by forces, such as stars in a galaxy or gas molecules in a container. It relates the average total kinetic energy of a system to its average total potential energy.