Newton's Law & Whiplash: How Headrests Protect Against Rear-End Collisions

Newton's first law of inertia states that an object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

When a car is hit from behind, the passengers' bodies are initially at rest. However, the car's sudden acceleration causes their bodies to continue moving forward at the same speed as the car. This forward motion causes the passengers' necks to hyperextend, which can lead to serious injuries.

A head restraint helps to prevent this type of injury by preventing the passenger's head from being thrown back too far. When a car is hit from behind, the headrest will support the passenger's head and neck and help to prevent hyperextension.