Originally Posted by
Alagaesian
Technically, in that situation, the DM could simply say that the rod would have such a high relative speed (kilometers per second!) that the rod is torn apart/vaporized by the sheer amount of air friction caused. Or, if those arguments are rendered invalid by magic, you could simply tell them that the speed was so incredible that it only punched a neat rod-shaped hole through the door and any intercepting walls before the planet moved onward. That IS what tends to happen when you fling a relatively small projectile at a massive speed through an amorphous material like wood or stone - a BB gun punches holes in paper, but doesn't rip it.