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chapter 4 : Statics -Torques and Equilibirum

Statics -Torques and Equilibrium

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chapter 4 : Statics -Torques and Equilibirum

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  1. Chapter 4: Statics (نوﻛﺳﻟا مﻠﻋ) Torques and Equilibrium Torques and Equilibrium (نازﺗﻻا و موزﻌﻟا)

  2. Outline ? 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)

  3. Introduction ? 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).

  4. Torques ?

  5. Torque

  6. Examples

  7. Conditions for a rigid body equilibrium: ?

  8. Types of equilibrium: ? 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

  9. Example

  10. Example 2

  11. Stability and Balance

  12. Example ? 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.

  13. A person clenching a bullet between his teeth

  14. Solution ?

  15. Lever in Human Body

  16. Lever in Human Body

  17. Lever in Human Body

  18. Lever in Human Body

  19. Lever in Human Body

  20. Lever in Human Body

  21. Glossary ? 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

  22. Exercise 4-13 ? 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.

  23. Solution ?

  24. Types of Levers

  25. Exercise 37 ? The head pivots about the atlanto-occipital 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

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