Some of the physics
Neither the mass nor the density of the object that fell off affect the total energy delivered to the structure. The relevant quantities are the area of the fragment presented to the slipstream, the dynamic unit pressure at the prevailing flight conditions and the distance between the point of detachment and the point of impact. From this must be subtracted the energy remaining in the fragments immediately after impact.
Assessing the potential for damage is far more difficult as it involves the area of impact and the strength and rigidity of both the fragment and the structure.