How do Hockey/American Football helmets work?

tl:dr - The goal is to reduce the force on the players head, by increasing the amount of time the impact takes. And to reduce the elasticity of the collision, to reduce the ratting around of the brain. 1. read more

Construction helmets are of this type, and do a fine job when somebody drops a brick on your head or you bump hard against an overhanging steel beam. Just don't fall off a bicycle with one, since they will not handle the impact of falling on pavement. The foams in some helmets are crushable but do not ever recover. read more

tl:dr - The goal is to reduce the force on the players head, by increasing the amount of time the impact takes. And to reduce the elasticity of the collision, to reduce the ratting around of the brain. read more