7. The main muscles that hold your head upright attach to your spine in back of

Question

7. The main muscles that hold your head upright attach to your spine in back of the point where your head pivots on your neck. The distances to the muscle attachment from this pivot and from the center of gravity of the head are shown in Figure P8.66. The muscles pull down to keep your head upright. If the muscle relaxes—if, for instance, you doze in a one of your other classes besides Physics—your head tips forward. If your head has a mass of 4.8 kg, what muscle force is needed to keep your head from tipping forward?

Edit: forgot to add picture ^

Explanation / Answer

In equilibrium net torque = o

let F be the muscle force

weight of the head w = mg = 4.8*9.8

F*0.05 - W*0.042 = 0

F*0.05 - (4.8*9.8*0.042) = 0

F = 39.5 N

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