Hints, please? "An arterial aneurysm is a life threatening condition associated with a balloon like expansion of a local segment of an artery. Using a free body diagram determine the average wall stresses in a closed spherical aneurysm with wall thickness h and inner radius [itex]r_i[/itex]. Ignore blood flow for this purpose." Intuitively, it makes sense that an increased stress would decrease the wall thickness h, making for a more unstable aneurysm. I would imagine an equation relating the normal wall stress and wall thickness as inversely proportional quantities, but once again as usual I'm having trouble squeezing the actual mathematical statements out of the info given. A head-start maybe?