Angu58

@wburnes: That's not it. When a light and a heavy helmet hit an object that doesn't move, then forces are the same, eg. hitting the ground or a rock. However, if the object that is hit has any movement or compressibility, then the heavier helmet will perform better due to higher mass lowering the maximum deceleration force experienced. For a light vs heavy helmet, the heavy will perform equal or better depending on the object struck. Throw a ping pong ball and a steel ball bearing at a cement block -- assuming same velocity, the deceleration force experienced should be the same, as there is no compression in the block. But, throw them both at a styrofoam board, and the ping pong ball will be stopped immediately, with higher g-force, while the ball bearing either passes through completely, or comes to a stop after some distance travelled through the wall.

Increasing mass of the helmet will not increase force transferred to the brain. It will transfer more energy to the dirt or tree you hit, but more mass=more inertia for your head, and slower deceleration upon impact. Slower deceleration means lower risks of concussion.