The mechanism of a rear-end collision starts with the basics physics principles established by Newton: a mass at rest remains at rest until acted upon by some external force; and a mass in motion remains in motion until acted upon by some external force. The laws of physics demonstrate that rear-end collisions produce a sudden acceleration, which is transmitted through the car seat to the victim’s body.
The bead, being a mass at rest, remains at rest until acted upon by the rear-ending force. The great flexibility of the neck, combined with the resting weight of the head (8 – 12 lbs) + rear-ending force results in a forceful hyperextension of the neck as the body is accelerated forward.
When the head hits the top of the headrest, this impact, plus the reflex contraction of the neck muscles, start the head in forward motion. The head continues forward until it comes into contact with the wheel or windshield, or, as in cases where seat belts are worn, restraining action of the soft tissue structures which hold the head and neck on the body. This type of injury tends to stretch and tear the soft tissue that limit extension and flexion. The result: soft-tissue whiplash.