Hello.

I was in the backseat of my mom's car yesterday (she was driving) and we were going about 50 miles per hour. The light turned yellow so we came to an abrupt stop. I had my hand on the handle the entire ride and I believe I put my other hand on the same handle as well once I sensed that we were coming to a fast stop. The force of the stop wasn't enough to snap my head back and then forward; however, I believe that my head was tilted forward by the stop.

Does it sound like I have a sub-concussive injury?

Thanks for the input, I really appreciate it!

You cannot suffer an head injury in the car unless the car has hit a solid object. This also was not a sub-concussive impact.

The only way there is risk of injury without hitting a solid object (another vehicle) is when the road is violently rough and you drive down that rough road for a few minutes of continuous shaking. This is unreasonable because the driver could just slow down to get past the rough area after the first few bumps.

Thanks Mark! However, I thought that you could sustain a brain injury if someone slams the brakes and your head slams forward (even if your head doesn't hit anything).

No, the braking action of a car is limited to about 1.5 G's. That will not cause a concussion. If you weight 150 pounds, your weight against the seat belt will max out at 225 pounds. Your 8 pound head will feel like it weighs 12 pounds. Laying your head on a pillow carefully is 8 pounds (1 G). Plopping your head on a pillow can easily be 4 or 5 G's or more. Subconcussive impacts generally start at 20 G's for very sensitive brains and 40 to 50 G's or more for normal brains.

If you are caught off guard and your head whipped forward until your seat belt stopped your forward movement, you might experience a few more G's due to the whipping effect. But, if you resisted the braking action, the G force would not exceed 1.5.

Thanks again Mark! However, I've been told that my head is pretty big (I personally thinks it's very big as well). Do you think my big head could have made me sustain a sub-concussive impact? Oh and I weigh about 155 pounds, do you think my weight could have made me sustain a sub-concussive impact?

Your weight or the size of you head has no bearing on the forces. G forces are about acceleration and deceleration. Your deceleration will be the same regardless of your weight.

1.5 G's against the seat belt means a body that weights 150 pounds will exert 225 (1.5 times 150 lbs) against the seat belt. The 1.5 G limit is due to the limit of braking traction the tires have. Your 155 pound body would exert 232.5 pounds against the seat belt.

It is not the weight that damages. It is the rate of deceleration.

There is a saying. Jumping out of an airplane is not dangerous. It is the risk of a sudden stop that is. The fall doesn't kill you. The sudden stop does. A stunt man can jump from extreme heights if he lands on an airbag that slows his deceleration at the bottom..

If you do not understand the basic of the laws of physics, then you need to just try to accept that I do and you did not sustain a concussive force or even a sub-concussive force.

PLUS, it takes HUNDREDS of sub-concussive forces over a few weeks or less to cause a cumulative injury.

Thank you Mark ! And yeah, I know nothing about physics