1D Motion & Kinematics - Physics 101 / AP Physics 1 Review with Dianna Cowern

Your head is already a helmet, and evolution mitigated the rapid deceleration problem as best it could.  Crash helmets amplify, and improve upon, the solution evolution arrived at for direct impact deceleration (ie. the skull and the ‘padding’ of cerebral fluid) but in so doing they undo the solution that evolution achieved for mitigating fatal brain injury caused by the torquing forces that are applied by a glancing blow.  An off centre blow to a helmet strapped securely to your head causes your skull to rotate at the same speed as the helmet.  This speed, if sufficient, could leave your fluid suspended brain a victim of its own inertia; creating fatal torsion at the brain stem.  Evolution addressed this problem by giving us a flexible (and if all else fails, tearable) scalp.  Some of the energy from an off centre impact is absorbed by the pliant elastic scalp, lessening the rotational acceleration of the skull, in turn lessening the torc applied to the brain stem.  A better crash helmet would have a deformable artificial ‘scalp’.