The change in velocity that occurs is set by the initial driving speed and the mass of the head doesn’t change during the collision, so according to the previous equation, the impulse experienced by t...The change in velocity that occurs is set by the initial driving speed and the mass of the head doesn’t change during the collision, so according to the previous equation, the impulse experienced by the head is known. More importantly, the compressing seat reduces the distance between the body and the head-rest during a rear-end collision and provides more time over which the headrest can move the head to keep up with the body.
