Even when the head is held erect, as in the figure below, its center of mass is not directly over the principal point of support (the atlanto-occipital joint, point A). The muscles at the back of the neck should therefore exert a force to keep the head erect. That is why your head falls forward when you fall asleep in the class. If the head weighs 43 N, calculate the force exerted by the muscles, FM, using the information in the figure.
I have no idea how to even begin solving this problem. If someone could help me out and maybe even just give me some direction or outline the steps that would be awesome!
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