For a healthy individual with no hair diseases, hair fiber is very strong, as strong as copper wire of the same diameter, so the key weak spot is the strength by which the hair fiber is anchored in the hair follicle in the skin. So as you can see hair is incredibly strong. It also has elastic properties. It can stretch up to 20% of its original length before breaking when it is dry and when it is wet it may stretch up to 50% before breaking. So how does hair break if it is so strong? It depends on the speed at which the pulling force is applied to the hair. If you pull on hair slowly and steadily with gradual increasing force the hair will resist for quite some time before breaking. But if you apply sudden force and yank on the hair it will break. The tensile strength of the hair is reduced, the hair has no time to respond and stretch, which distributes the force over the length of the hair fiber, and the hair just snaps. So despite the apparent strength of hair, it will break if you brush or comb too vigorously because this applies a sudden force to the hair. Can you hang by your hair? The short answer is yes as you can see circus artistes hang by their hair and there is a long history in the circus world of these feats of hair strength dating all way back to ancient Chinese Empire. The primary limiting factor in whether someone can hang by their hair is the strength of their neck rather than the strength of their hair.