Danny,

We were doing more of a hypothetical calculation based on assumed values. There was never any expectation of a prefect answer.

There are not random errors in the calculations. The calculations are accurate. I calculate them multiple times in different orders. Only the values used have variability. Even the researchers who research helmet protection levels and the forces needed to cause a concussion have to make some assumptions.

If you read the thread from the start, you will see the comments about the assumptions made. The point is to put some basic understanding to how these forces work and how different variables effect the G forces. At least the calculations answer some of the questions, even if not perfectly.

** I am willing to explain the many issues. I did these calculations the first time over a decade ago. I am well aware of the inaccuracy involved. But, there is still value to understanding how these forces change.

I meant no offense. Please let others decide if my input adds to the conversation or not.

Shouldn't I be allowed to share my opinion without being dismissed?

Just to set the record straight, the many variables involved are:

If the head is the moving object.

The starting velocity of the head.
The ending velocity of the head.
The combined deflection/distortion of the head and object hit.
This can include padding of a hat, dashboard, etc. or flexing of a wall or
movement of the object.
Any angle of incidence (The angle the head was traveling compared to the
surface of the object.)
The time of head contact with the object surface until reaching the ending
velocity. Knowing the combined deflection/distortion makes this value
not critical.
Any rebound/bounce of the head. This is a difficult value to calculate and
add to the formula

If the head starts stationary and the object is moving.

The velocity of the object before contact with the head.
The velocity of the object after the contact.
The deflection/distortion of the object.
The deflection/movement of the head and angle of movement.(related to
the angle of incidence)
The weight of the object.
The weight of the head. (5000 grams is commonly used)
The weight of the object and weight of the head can be used to
determine the movement of the head. The deflection of the object is
still needed.
Any stabilizing forces holding the head in place. This is a value that is hard
to determine and a complex to add into the formula. It is not likely to
make a big difference in the end result.
The angle of incidence.

There may be some other variables but they would not change the value by much in most situations, such as, did the head start to rotate ?

Most of these values will be estimations or assumptions. But, by using highs and lows, a range of G forces can be calculated.

Absolutely!

I have done some edits accordingly

Today was the first time since a couple of weeks, where I got an impact to the head. it is difficult to explain what happened. I was in a restaurant and wanted to take my daily pills. I layed them town on an empty dish and tried to pick them up directly with my mouth(because my hands were dirty). I forgot that i was wearing a cap at that moment. So I tried to bend down, when suddenly the bill of the cap stopped my head as it hit the table. Maybe this doesn't sound bad for you, but I was moving down pretty quickly (About 1.5 or 2 m/s) and after the incident I got a strange feeling in my head.

I don't know excactly what numbers you need to do the calculation, but i give you all I can remember. There is a gap between my forehead and the innerside of the cap (about 3mm). I guess this cushioned the impact at least a bit.The table itself didn't move at all of course. my head was 30cm away from the table when it started to move down.

From the number you provided, I can only give you a high and low estimation. It looks like the low would be about 10 G's with a high of possibly 30 G's. I doubt you experienced the higher G's.

what parameters would you need to calculate it?

Mark, do you think the hardness of the colliding object also makes a difference to the Gs apart from speed ? For instance, I hit my head on a cement wall and not table with roughly same speed of 2m/s. What do you think G would be in my case ?

Also one thing I don't understand. Technicality, if the brain bounces back and forth after a concussion , then how do lower forces make it bounce back and forth after a single concussion ? For example let's assume a person has had a concussion with a 40G force which let's assume is enough to bounce a brain back and forth. Now this person has had a few more concussions after that and his brain is super sensitive yo even lower G forces. Does that mean now even with 10G force his brain will bounce back and forth ? This sounds crazy to me. Or is it some chemical balance that is disrupted more easily with each successive concussion and not necessarily bouncing back and forth phenomenon?

Hitting a concrete wall at the same speed as hitting a table would cause a higher G force because there would be less deflection ( absorption like a pillow would provide or how a table would move)

Why do you think your speed was 2 m/s ?

Your long question does not make sense to me. You are making assumptions about coup-contracoup (bouncing back) that are not necessarily related to G force.

A lot of coup-contracoup effect is because the head/skull bounces back causing the brain to hit the opposite side of the skull.

You are confusing/combining too many different concepts.

I want to add a quick question to this thread.

While sneezing, the head usually moves forward very quickly. This resultd often in an unpleasant pressure feeling in the head afterwards.

Because of that I formed the habit to fix my head with my hands, so that it can't move forward. Indeed it does move forward at least a bit, a complete prevention is just not possible. I wonder if the fixing with the hands even highers the forces on the head, because they stop the head earlier than in it's natural movement while sneezing.

However I have to admit that, from my experience, these method prevents the pressure feeling afterwards.