The Ehrenfest theorem, named after Austrian theoretical physicist Paul Ehrenfest, relates the time derivative of the expectation values of the position and momentum operators x and p to the expectation value of the force F = − V ′ {\displaystyle F=-V'} on a massive particle moving in a scalar potential V {\displaystyle V}, The Ehrenfest theorem is a special case of a more general relation between the expectation of any quantum mechanical operator and the expectation of the commutator of that operator with the Hamiltonian of the system where A is some quantum mechanical operator and ⟨A⟩ is its expectation value. Wikipedia