is known (IG), the inertia about any other point may be calculated with
the parallel-axis theorem as
IP = IG +md*d (d squared. The carrot up symbol does something to the post),
where d is the distance between G and P.
IG=(mL*L)/12 (Inertia about the mass center)
If the bar is fixed on the end, you are looking for the inertia from the end of the bar (IA)