The Masseter Muscle The masseter muscle, the principal muscle for chewing, is on

Question

The Masseter Muscle The masseter muscle, the principal muscle for chewing, is one of the strongest muscles for its size in the human body(Figure 1) . It originates on the lower edge of the zygomatic arch (cheekbone) and inserts in the angle of the mandible.

http://session.masteringphysics.com/problemAsset/1125529/5/5416311080_1.jpg

Figure 1 above

http://session.masteringphysics.com/problemAsset/1125529/5/5416311080_2.jpg

Figure 2 above

Find the biting force, FB, exerted on the mandible by the upper teeth.

The masseter muscle, the principal muscle for chewing, is one of the strongest muscles for its size in the human body(Figure 1). It originates on the lower edge of the zygomatic arch (cheekbone) and inserts in the angle of the mandible.

Explanation / Answer

A. since FM=500N

torque exerted by FM=500cos26 *3=1348.2 Nm

B.Since the mandible is in static equilibrium

Torque about the axis of rotation =0

==>FM (cos26.0)*(10.7-7.7)=FB*10.7

==>FB=500cos26.0 * 3/10.7=126N

FM cos(26.0)=FB=449.4N (balancing forces along the vertical axis)

Therefore torque produced about the axis of rotation=FB*10.7-FMcos26*(10.7-7.7)=449.4*7.7/100=34.61Nm.............ANS

C.Horizontal component of Fj=FMsin26=219.19N

D.vertical component of Fj=-(FMcos26-FB)=-323N...................ANS

'-' sign is indicated because the upward direction is considered as positive

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