Unless you strike your head against a solid surface as the car stops or the car hits a solid object at high speed, one cannot experience more than 2 Gs stopping a car. The brakes and tires will not cause more than 2 Gs.

Can somebody please answer a question?

Where are people getting the idea that fast stops in the car or bumping a wall or laying down hard onto a pillow or bed could be a concussion or cause damage?

Is there a Twitter feed or other social media that is spouting this nonsense?