Brain teaser for you. There is a powerful magnet fixed in place. You have an iron rod of great length and a paperclip. The rod is just light enough to be able to hang from the magnet. If the rod were even one centigram heavier, the magnet would not be strong enough to hold it up.
You hang the rod from the magnet, then you hang the paperclip from the magnet as well. What happens to the rod?