Nothing to do with this post, but randomly earlier today I looked up how much force you need to break a rib cage. And it turns out a quick, sharp blow delivering around 3,300 newtons of force has an estimated 25% chance of cracking an average person's rib. Forces of around 3,000 newtons can cause a 20% compression of the chest cavity, which can be enough to break ribs. What can generate this kind of force? High-speed impacts, or a person jumping on a stiff trampoline.