Originally Posted by
bbbean
Oh I agree! but when one spherical object is rotating relative to an enclosed sphere, it really doesn't matter whether you say the head rotated relative to the helmet or the helmet rotated relative to the head. The point was that a limited slip in the system dampened rotational forces.
It totally matters because of the force vectors. The entire point is to redirect impact force into moving the helmet and minimizing that force moving the head.
Again, reading the MIPS site I linked above is quite instructive and helpful.