Question
Asked Oct 15, 2019
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Even when the head is held erect, as shown in the figure, 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 55 N, calculate the force exerted by the muscles ?M using the information in the figure. Assume that ?1=5.3 cm, ?2=2.5 cm, and ∣∣?⃗ w∣∣=55 N. What is the force FJ exerted by the pivot on the head?

M
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Expert Answer

Step 1

Given information:

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5.3 cm x2.25 cm F 55 N

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Step 2

Take the moment about point A by considering counter clock wise direction as positive and plug ...

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ΣΜ- Fм*, — Fwx, 3D0 FyX М, —0 W F М х (55 N)(2.25 cm) Fм 5.3 cm F 23.35 N

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