Solution
= Solution
For $I=\frac12\sum m_i|x_i|^2$, differentiation gives
$$
\ddot I=2T+\sum_i x_i\mathbin\cdot F_i=2T+V,
$$
because the Newtonian potential is homogeneous of degree $-1$. Bounded positions and velocities imply $\overline{\ddot I}=0$, so the <virial theorem> gives $\overline T=-\overline V/2$.