So this question I have is so obvious that it's probably not even worth talking about from a scientific point of view but I just can't keep it out of my head. The moderators are welcome to delete this if they think it's too silly. Suppose there is a person tied to the windshield of a car. When the car starts moving, the person wouldn't feel much force from it and wouldn't be hurt that bad. However, if the person was standing still on the road and the car collided with him with the same force, he's going to be hurt pretty badly. Of course I don't have any actual experience with such a situation and I can not say that tying a person to a car and moving them around won't hurt the same, but intuitively I feel it won't. So if I am right in my conjecture, why is a collision more dangerous if the forces involved are the same?