Statics Torques and Equilibrium
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? Torques (موزﻌﻟا)
? Equilibrium of Rigid Bodies
ﺔﺑﻠﺻﻟا
ﺔﺋﺳﺎﺟﻟا مﺎﺳﺟﻻا نزاوﺗ

(
)
? The Center of Gravity (لﻘﺛﻟا زﻛرﻣ)
The Center of Gravity (لﻘﺛﻟا زﻛرﻣ)
? Stability and Balance (نزاوﺗﻟا و رارﻘﺗﺳﻻا)
? Levers; Mechanical Advantage
ﺔﯾﻟﻻا ةدﺋﺎﻔﻟا
ﻊﻓاورﻟا
(
:
)
? Muscles (تﻼﺿﻌﻟا)
? Levers in the Body (ﺔﯾﺣﻟا تﺎﻧﺋﺎﻛﻟا مﺳﺟ ﻲﻓ ﻊﻓاورﻟا)
? Statics is the study of the forces acting on an
object that is in equilibrium and at rest.
? Engineering structures: Bridges or buildings
Biological structures : Jaws (كﻔﻟا),
? Biological structures : Jaws (كﻔﻟا),
limbs(فارطا), or backbones(يرﺎﻘﻔﻟا دوﻣﻌﻟا).
? Engineering, comparative anatomy( ﺢﯾرﺷﺗ
نرﺎﻘﻣ), physical therapy(
ﻲﻌﯾﺑط
ﻟا جﻼﻌﻟا
), and
orthodonture (نﺎﻧﺳﻻا مﯾوﻘﺗ).
?
? static equilibrium: a state of equilibrium in
which the net external force and torque acting
on a system is zero
? dynamic equilibrium: a state of equilibrium in
which the net external force and torque on a
system moving with constant velocity are
zero
? Unlike most of the other muscles in our
bodies, the masseter muscle(ﺔﻐﺿﺎﻣﻟا ﺔﻠﺿﻌﻟا) in
the jaw, as illustrated in next slide, is
attached relatively far from the joint, enabling
attached relatively far from the joint, enabling
large forces to be exerted by the back teeth.
(a) Using the information in the figure,
calculate the force exerted by the teeth on
the bullet.
(b) Calculate the force on the joint.
between his teeth
?
? Torque: turning or twisting effectiveness of a
force
? Perpendicular lever arm: the shortest distance
from the pivot point to the line along which F
lies
lies
? SI units of torque: newton times meters,
usually written as N·m
? Center of gravity: the point where the total
weight of the body is assumed to be
concentrated
? Find the force F1 and F2 on the tooth in fig.
4.36 (In orthodonture, forces applied to the
teeth lead to forces on the supporting bones,
Gradually the bone tissue breaks down and
Gradually the bone tissue breaks down and
permits the tooth to rotate or translate. New
bone tissue grows in the space left behind.
The forces must be small enough to avoid
damaging the root of the tooth.
?
? The head pivots about the atlantooccipital
joint (Fig.4.46). The splenius muscles
attached behind the joint support the head.
(a) What class of lever does this represent?
(a) What class of lever does this represent?
Class 1
(b) The anterior muscles (ﺔﯾﻣﺎﻣﻻا تﻼﺿﻌﻟا)produce
forward motions of the head. What class of
levers does their action represent? Class 3