Forces on and in the Body PDF

 Forces on and in the Body Introduction We are usually unaware of important forces in the body, for example, the muscular forces that cause the blood to circulate and the lungs to take in air. In the bones there are many crystals of bone mineral (calcium hydroxyapatite) that require ca...

 Forces on and in the Body Introduction We are usually unaware of important forces in the body, for example, the muscular forces that cause the blood to circulate and the lungs to take in air. In the bones there are many crystals of bone mineral (calcium hydroxyapatite) that require calcium. A calcium atom will become part of the crystal if it gets close where the electric forces are great enough to trap it. It will stay in that place until the electrical forces can no longer hold it in place if the bone crystal is destroyed by cancer. ‫ﻣﻘﺪﻣﺔ‬ ‫ اﻟﻘﻮى‬،‫ ﻋﻠﻰ ﺳﺒﯿﻞ اﻟﻤﺜﺎل‬،‫ﻧﺤﻦ ﻋﺎدة ﻻ ﻧﺪرك اﻟﻘﻮى اﻟﻤﮭﻤﺔ ﻓﻲ اﻟﺠﺴﻢ‬ ‫ ﯾﻮﺟﺪ ﻓﻲ‬.‫ﻌﻀﻠﯿﺔ اﻟﺘﻲ ﺗﺴﺒﺐ دوران اﻟﺪم واﺳﺘﻨﺸﺎق اﻟﮭﻮاء إﻟﻰ اﻟﺮﺋﺘﯿﻦ‬ ‫ﻌﻈﺎم اﻟﻌﺪﯾﺪ ﻣﻦ ﺑﻠﻮرات ﻣﻌﺎدن اﻟﻌﻈﺎم )ھﯿﺪروﻛﺴﯿﺒﺎﺗﯿﺖ اﻟﻜﺎﻟﺴﯿﻮم( اﻟﺘﻲ‬ ‫ ﺳﺘﺼﺒﺢ ذرة اﻟﻜﺎﻟﺴﯿﻮم ﺟﺰًءا ﻣﻦ اﻟﺒﻠﻮرة إذا اﻗﺘﺮﺑﺖ‬.‫ﺗﺘﻄﻠﺐ اﻟﻜﺎﻟﺴﯿﻮم‬.‫ﻣﻦ ﻣﻜﺎن ﺗﻜﻮن ﻓﯿﮫ اﻟﻘﻮى اﻟﻜﮭﺮﺑﺎﺋﯿﺔ ﻛﺒﯿﺮة ﺑﻤﺎ ﯾﻜﻔﻲ ﻻﺣﺘﺠﺎزھﺎ‬ ‫وﺳﺘﺒﻘﻰ ﻓﻲ ذﻟﻚ اﻟﻤﻜﺎن ﺣﺘﻰ ﻻ ﺗﺘﻤﻜﻦ اﻟﻘﻮى اﻟﻜﮭﺮﺑﺎﺋﯿﺔ ﻣﻦ ﺗﺜﺒﯿﺘﮭﺎ ﻓﻲ‬.‫ﻣﻜﺎﻧﮭﺎ إذا ﺗﻢ ﺗﺪﻣﯿﺮ ﺑﻠﻮرة اﻟﻌﻈﺎم ﺑﺴﺒﺐ اﻟﺴﺮطﺎن‬ A: Forces in the Body 1. Gravitational Force G.F Newton’s law states that "there is a force of attraction between any two objects". This force is directly proportional to the product of the two masses and inversely proportional to the square of the distance between them. ‫ اﻟﻘﻮى ﻓﻲ اﻟﺠﺴﻢ‬:‫ج‬ ‫ف‬.‫ ﻗﻮة اﻟﺠﺎذﺑﯿﺔ ج‬.1 ‫ﯾﻨﺺ ﻗﺎﻧﻮن ﻧﯿﻮﺗﻦ ﻋﻠﻰ أن "ھﻨﺎك ﻗﻮة ﺟﺬب ﺑﯿﻦ أي‬ ‫ ھﺬه اﻟﻘﻮة ﺗﺘﻨﺎﺳﺐ طﺮدﯾﺎ ﻣﻊ ﺣﺎﺻﻞ ﺿﺮب اﻟﻜﺘﻠﺘﯿﻦ‬."‫ﻤﯿﻦ‬.‫وﻋﻜﺴﯿﺎ ﻣﻊ ﻣﺮﺑﻊ اﻟﻤﺴﺎﻓﺔ ﺑﯿﻨﮭﻤﺎ‬ Effects of gravitational force are: 1. Formation of varicose veins in the legs, as the venous blood travels against the force of gravity on its way to the heart. 2. The loss of some bone mineral, when a person becomes weightless such as in an orbiting satellite journey. 3. Long-term bed rest removes much of the force of body weight from the bone → can lead to a serious bone loss. 2. Electric Force E.F. Electrical forces are immense compared to gravitational force since it involves attractive and repulsive forces between electrical charges. For example E.F. between e – and p+ in H2 atoms (1039) time greater than G.F. :‫ﺗﺄﺛﯿﺮات ﻗﻮة اﻟﺠﺎذﺑﯿﺔ ھﻲ‬.‫ ﺣﯿﺚ ﯾﺘﺤﺮك اﻟﺪم اﻟﻮرﯾﺪي ﻋﻜﺲ ﻗﻮة اﻟﺠﺎذﺑﯿﺔ ﻓﻲ طﺮﯾﻘﮫ إﻟﻰ اﻟﻘﻠﺐ‬،‫اﻟﺪواﻟﻲ ﻓﻲ اﻟﺴﺎﻗﯿﻦ‬.‫ ﻓﻘﺪان ﺑﻌﺾ ﻣﻌﺎدن اﻟﻌﻈﺎم ﻋﻨﺪﻣﺎ ﯾﺼﺒﺢ اﻹﻧﺴﺎن ﻋﺪﯾﻢ اﻟﻮزن ﻣﺜﻞ رﺣﻠﺔ اﻟﻘﻤﺮ اﻟﺼﻨﺎﻋﻲ‬.2 ‫ﺔ ﻓﻲ اﻟﻔﺮاش ﻋﻠﻰ اﻟﻤﺪى اﻟﻄﻮﯾﻞ ﺗﺰﯾﻞ اﻟﻜﺜﯿﺮ ﻣﻦ ﻗﻮة وزن اﻟﺠﺴﻢ ﻣﻦ اﻟﻌﻈﺎم ← ﯾﻤﻜﻦ أن‬.‫ﺗﺆدي إﻟﻰ ﻓﻘﺪان اﻟﻌﻈﺎم ﺑﺸﻜﻞ ﺧﻄﯿﺮ‬.‫إف‬.‫ اﻟﻘﻮة اﻟﻜﮭﺮﺑﺎﺋﯿﺔ إي‬.2 ‫ﻮى اﻟﻜﮭﺮﺑﺎﺋﯿﺔ ھﺎﺋﻠﺔ ﻣﻘﺎرﻧﺔ ﺑﻘﻮة اﻟﺠﺎذﺑﯿﺔ ﻷﻧﮭﺎ ﺗﺘﻀﻤﻦ ﻗﻮى ﺗﺠﺎذب وﺗﻨﺎﻓﺮ ﺑﯿﻦ اﻟﺸﺤﻨﺎت‬.G.F ‫ ﻣﺮة أﻛﺒﺮ ﻣﻦ‬H2 (1039) ‫ ﻓﻲ ذرات‬+p‫ – و‬e ‫ ﺑﯿﻦ‬.E.F ‫ ﻋﻠﻰ ﺳﺒﯿﻞ اﻟﻤﺜﺎل‬.‫ﺮﺑﺎﺋﯿﺔ‬ There are two types of E.F.: A- Static force: (either attractive or repulsive). B- Magnetic force: (produced by moving electrical charge in muscle and nerves). The forces produced by the muscles are caused by electrical charges attracting or repelling other electrical charges. Living cells in the body has electrical potential difference across cell membrane because of a difference in charge between the inside and outside of the cell. This amounts to less than 0.1 V, but because of the very thin cell wall it may produce a field as large as 105 V/m. Electric eel is essentially weightless in the water and able to add the potential from many cells to produce several hundred volts. This special" cell battery" occupies up 80% of an eel's body length. :EF ‫ھﻨﺎك ﻧﻮﻋﺎن ﻣﻦ‬.(‫ )إﻣﺎ ﺟﺎذﺑﺔ أو ﺗﻨﺎﻓﺮﯾﺔ‬: ‫ اﻟﻘﻮة اﻟﺴﺎﻛﻨﺔ‬-‫أ‬ ‫ )ﺗﻨﺘﺞ ﻋﻦ ﺗﺤﺮﯾﻚ اﻟﺸﺤﻨﺎت اﻟﻜﮭﺮﺑﺎﺋﯿﺔ ﻓﻲ اﻟﻌﻀﻼت‬:‫ اﻟﻘﻮة اﻟﻤﻐﻨﺎطﯿﺴﯿﺔ‬-‫ب‬.(‫واﻷﻋﺼﺎب‬ ‫ﺘﺞ اﻟﻘﻮى اﻟﺘﻲ ﺗﻨﺘﺠﮭﺎ اﻟﻌﻀﻼت ﻋﻦ ﺷﺤﻨﺎت ﻛﮭﺮﺑﺎﺋﯿﺔ ﺗﺠﺬب أو ﺗﻄﺮد ﺷﺤﻨﺎت‬.‫ﻛﮭﺮﺑﺎﺋﯿﺔ أﺧﺮى‬ ‫ﺰ اﻟﺨﻼﯾﺎ اﻟﺤﯿﺔ ﻓﻲ اﻟﺠﺴﻢ ﺑﺎﺧﺘﻼف اﻟﺠﮭﺪ اﻟﻜﮭﺮﺑﺎﺋﻲ ﻋﺒﺮ ﻏﺸﺎء اﻟﺨﻠﯿﺔ ﺑﺴﺒﺐ‬ ‫ وﻟﻜﻦ‬،‫ ﻓﻮﻟﺖ‬0.1 ‫ ﯾﺼﻞ ھﺬا إﻟﻰ أﻗﻞ ﻣﻦ‬.‫ف اﻟﺸﺤﻨﺔ ﺑﯿﻦ داﺧﻞ اﻟﺨﻠﯿﺔ وﺧﺎرﺟﮭﺎ‬.‫م‬/‫ ﻓﻮﻟﺖ‬105 ‫ ﻗﺪ ﯾﻨﺘﺞ ﻣﺠﺎﻻً ﻛﺒﯿًﺮا ﯾﺼﻞ إﻟﻰ‬،‫ﺑﺴﺒﺐ ﺟﺪار اﻟﺨﻠﯿﺔ اﻟﺮﻗﯿﻖ ﺟًﺪا‬ ‫ﺛﻌﺒﺎن اﻟﺒﺤﺮ اﻟﻜﮭﺮﺑﺎﺋﻲ ﻋﺪﯾﻢ اﻟﻮزن ﺑﺸﻜﻞ أﺳﺎﺳﻲ ﻓﻲ اﻟﻤﺎء وﻗﺎدر ﻋﻠﻰ إﺿﺎﻓﺔ‬ ‫ ﺗﺸﻐﻞ ھﺬه "اﻟﺒﻄﺎرﯾﺔ‬.‫ﻣﻜﺎﻧﺎت اﻟﻌﺪﯾﺪ ﻣﻦ اﻟﺨﻼﯾﺎ ﻹﻧﺘﺎج ﻋﺪة ﻣﺌﺎت ﻣﻦ اﻟﻔﻮﻟﺘﺎت‬.‫ ﻣﻦ طﻮل ﺟﺴﻢ ﺛﻌﺒﺎن اﻟﺒﺤﺮ‬٪80 ‫اﻟﺨﻠﻮﯾﺔ" اﻟﺨﺎﺻﺔ ﻣﺎ ﯾﺼﻞ إﻟﻰ‬ 3. Nuclear Force N.F. A- Strong nuclear force: is larger than the other → its acts as the "glue" to hold the nucleus together against the repulsive force produced by the proton on each other. B- Weaker nuclear force: is involved with electron (beta) decay from the nucleus. ‫‪.‬‬ ‫‪.3‬اﻟﻘﻮة اﻟﻨﻮوﯾﺔ ‪NF‬‬ ‫أ‪ -‬اﻟﻘﻮة اﻟﻨﻮوﯾﺔ اﻟﻘﻮﯾﺔ‪ :‬أﻛﺒﺮ ﻣﻦ اﻷﺧﺮى → ﺗﻌﻤﻞ ﺑﻤﺜﺎﺑﺔ "اﻟﻐﺮاء" اﻟﺬي ﯾﺮﺑﻂ اﻟﻨﻮاة‬ ‫ﺑﺒﻌﻀﮭﺎ اﻟﺒﻌﺾ ﺿﺪ اﻟﻘﻮة اﻟﺘﻨﺎﻓﺮﯾﺔ اﻟﺘﻲ ﯾﻨﺘﺠﮭﺎ اﻟﺒﺮوﺗﻮﻧﺎت ﻋﻠﻰ ﺑﻌﻀﮭﺎ اﻟﺒﻌﺾ‪.‬‬ ‫ب‪ -‬اﻟﻘﻮة اﻟﻨﻮوﯾﺔ اﻷﺿﻌﻒ‪ :‬وﺗﺸﺎرك ﻓﻲ اﺿﻤﺤﻼل اﻹﻟﻜﺘﺮون )ﺑﯿﺘﺎ( ﻣﻦ اﻟﻨﻮاة‪.‬‬ ‫‪B: Forces on the body‬‬ ‫‪1. Static Forces:‬‬ ‫‪When objects are stationary, the sum of the forces and the‬‬ ‫‪sum of the torques about any axis is equals zero.‬‬ ‫‪Many of the muscle and bone systems of the body act as‬‬ ‫‪levers which are classified to:‬‬ ‫)‪A- First class lever: the force at the fulcrum point (F‬‬ ‫‪between the muscle force (M) and the weight (W) (e.g. the‬‬ ‫‪head).‬‬ ‫ب‪ :‬اﻟﻘﻮى اﻟﻤﺆﺛﺮة ﻋﻠﻰ اﻟﺠﺴﻢ‬ ‫‪.1‬اﻟﻘﻮى اﻟﺴﺎﻛﻨﺔ‪:‬‬ ‫ﻷﺟﺴﺎم ﺛﺎﺑﺘﺔ‪ ،‬ﻓﺈن ﻣﺠﻤﻮع اﻟﻘﻮى وﻣﺠﻤﻮع ﻋﺰم اﻟﺪوران ﺣﻮل أي ﻣﺤﻮر‬ ‫ﯾﺴﺎوي ﺻﻔًﺮا‪.‬‬ ‫ﻌﻤﻞ اﻟﻌﺪﯾﺪ ﻣﻦ أﺟﮭﺰة اﻟﻌﻀﻼت واﻟﻌﻈﺎم ﻓﻲ اﻟﺠﺴﻢ ﻛﺮاﻓﻌﺎت وﺗﺼﻨﻒ إﻟﻰ‪:‬‬ ‫ﺔ اﻷوﻟﻰ‪ :‬اﻟﻘﻮة ﻋﻨﺪ ﻧﻘﻄﺔ اﻻرﺗﻜﺎز )‪ (F‬ﺑﯿﻦ اﻟﻘﻮة اﻟﻌﻀﻠﯿﺔ )‪ (M‬واﻟﻮزن‬ ‫)‪) (W‬اﻟﺮأس ﻣﺜﻼً(‪.‬‬ B- Second class lever: W between F and M (e.g. standing on toes). ‫ )ﻣﺜﻞ اﻟﻮﻗﻮف ﻋﻠﻰ أﺻﺎﺑﻊ‬M‫ و‬F ‫ ﺑﯿﻦ‬W :‫ راﻓﻌﺔ اﻟﺪرﺟﺔ اﻟﺜﺎﻧﯿﺔ‬-‫ب‬.(‫اﻟﻘﺪم‬ C- Third class lever: M between F and W (e.g. the elbow joint of the.(‫ )ﻣﺜﻼً ﻣﻔﺼﻞ اﻟﻜﻮع ﻟﻠﺬراع‬W‫ و‬F ‫ ﺑﯿﻦ‬M :‫ راﻓﻌﺔ ﻣﻦ اﻟﺪرﺟﺔ اﻟﺜﺎﻟﺜﺔ‬-‫ج‬ A simple example of a lever system in the body: :‫ﻣﺜﺎل ﺑﺴﯿﻂ ﻟﻨﻈﺎم اﻟﺮاﻓﻌﺔ ﻓﻲ اﻟﺠﺴﻢ‬ (a) The arm in equilibrium with neglect the weight of forearm and hand H, there are only two torques. 4M – 30W=0 M = 7.5 W (b) The arm in equilibrium with taking the weight of the forearm and hand. A typical value of H (15 N). 4M – 14H – 30W =0 M= 3.5H + 7.5W By taking the sum of the torques about the shoulder joint, the tension T can be calculated from:.‫ ﻓﻼ ﯾﻮﺟﺪ ﺳﻮى ﻋﺰﻣﯿﻦ‬،H ‫)أ( اﻟﺬراع ﻓﻲ ﺣﺎﻟﺔ اﺗﺰان ﻣﻊ إھﻤﺎل وزن اﻟﺴﺎﻋﺪ واﻟﯿﺪ‬ 0=‫ وات‬30 – ‫ م‬4 ‫ واط‬7.5 = ‫م‬.H (15 N) ‫ ﻗﯿﻤﺔ ﻧﻤﻮذﺟﯿﺔ ﻟـ‬.‫)ب( ﺗﻮازن اﻟﺬراع ﻣﻊ وزن اﻟﺴﺎﻋﺪ واﻟﯿﺪ‬ 0= ‫ وات‬30 – ‫ ﺳﺎﻋﺔ‬14 – ‫ م‬4 ‫ واط‬7.5 + ‫ ﺳﺎﻋﺔ‬3.5 = ‫م‬ T ‫ ﻓﺈن اﻟﺘﻮﺗﺮ‬،‫ﻣﻦ ﺧﻼل أﺧﺬ ﻣﺠﻤﻮع ﻋﺰم اﻟﺪوران ﺣﻮل ﻣﻔﺼﻞ اﻟﻜﺘﻒ‬ :‫ﯾﻤﻜﻦ ﺣﺴﺎﺑﮭﺎ ﻣﻦ‬ The calculated force at the fifth lumbar vertebra (L5) with the body tipped forward at 60 degree to the vertical and with a weight of 225N in the hands can approach 3800N. A hollow needle connected to a calibrated pressure transducer is inserted into the gelatinous center of intervertebral discs in order to measure the pressure in the discs separating the vertebrae. If the disc is over loaded in a lifting accident it can rupture, causing pain either from the rupture or by allowing irritating materials from inside the disc to leak out. Sometimes vertebral bone collapse rather than disc damage occurs. This often happens in elderly woman who suffer from weakened bones. Collapse of a vertebra can lead to hunchback stature ‫ٮزاويﺔ‬, ‫ﺤﺴﻢ ﻟﻸﻣﺎم‬,‫ٮﻞ اﻟ‬5‫( ﻣﻊ ﻣ‬L5) ‫ﺤﺎﻣﺴﺔ‬/‫ٮﺔ اﻟ‬5‫ٮ‬/‫ڡﻄ‬$‫ڡﺮة اﻟ‬$‫ڡ‬/‫ى اﻟ‬1‫ڡ‬/ ‫ٮﺔ‬,‫ڡﻮة اﻟﻤﺤﺴو‬$‫اﻟ‬ ‫ٮﺮب ﻣﻦ‬$‫ڡ‬$$‫ﻤﻜﻦ أن ٮ‬5 ‫ﻦ ٮ‬5 ‫ٮﺪٮ‬5‫ى اﻟ‬1‫ڡ‬/ ‫ﻦ‬$‫ٮﻮٮ‬5‫ٮ‬/ 225 ‫ﺣﺔ إﻟﻰ اﻟﻮﺿﻊ اﻟرأﳼ وﻣﻊ وزن‬,‫ در‬60.‫ﻦ‬$‫ٮﻮٮ‬5‫ٮ‬/ 3800 ‫ڡراص‬$‫ٮﲏ ﻟﻸ‬5$‫ٮﻼٮ‬5‫ﺤ‬,‫ى اﻟﻤﺮﻛﺰ اﻟ‬1‫ڡ‬/ ‫ﺮ‬5 ‫ﻌﻂ ﻣﻌﺎٮ‬U‫ٮﻤﺤول ﺿ‬, ‫ٮﺼﻠﺔ‬$‫ڡﺔ ﻣ‬/‫ﺤﻮ‬,‫ٮﺮة ﻣ‬,‫ﺣﺎل إ‬/‫ٮﻢ إد‬$5 ‫ٮ‬.‫ڡرات‬$‫ڡ‬/‫ٮيﻦ اﻟ‬, ‫ڡﺼﻞ‬/$‫ڡراص اﻟﱵ ٮ‬$‫ى اﻷ‬1‫ڡ‬/ ‫ﻌﻂ‬U‫ٮﺎس اﻟﻀ‬5‫ڡ‬$ ‫ﺣﻞ‬,‫ڡريﺔ ﻣﻦ أ‬$‫ڡ‬/‫اﻟ‬ ‫ ﻣﻤﺎ‬،‫ﺤﺮ‬,‫ڡ‬/‫ٮ‬/5 ‫ڡﻤﻦ اﻟﻤﻤﻜﻦ أن ٮ‬/ ،‫ڡﻊ‬/‫ى ﺣﺎدث ر‬1‫ڡ‬/ ‫ٮﺮ ﻣﻦ اﻟﻼزم‬c‫ڡﺮص أﻛ‬$‫ٮﻞ اﻟ‬5‫ﺤﻤ‬$‫ﻢ ٮ‬$‫إذا ٮ‬ ‫ﺣﻞ‬/‫ﺤﺔ ﻣﻦ دا‬,‫ٮ‬5‫ٮﻤزق أو ﻋﻦ ﻃريﻖ اﻟﺴﻤﺎح ﻟﻠﻤواد اﻟﻤﻬ‬$‫ٮﺐ اﻷﻟﻢ إﻣﺎ ﻣﻦ اﻟ‬,‫ﺴ‬5 ‫ٮ‬.‫ٮﺴﺮب‬$‫ٮﺎﻟ‬, ‫ڡﺮص‬$‫اﻟ‬ ‫ﺤﺪث ﻫﺬا‬5 ‫ ٮ‬.‫ڡﺮص‬$‫ﻠﻒ اﻟ‬$‫ٮﺪﻻ ً ﻣﻦ ٮ‬, ‫ڡري‬$‫ڡ‬/‫ﻄﻢ اﻟ‬/‫ٮﺎر اﻟﻌ‬5‫ٮﻬ‬/‫ﺤﺪث ا‬5 ‫ٮﺎن ٮ‬5‫ٮﻌﺾ اﻷﺣ‬, ‫ى‬1‫ڡ‬/ ‫ ٮ "ﻤﻜﻦ أن ٮ "ﺆدي‬.‫ى ٮ "ﻌﺎ*ٮ"ٮﻦ ﻣﻦ ﺿﻌﻒ اﻟﻌ*ﻄﺎم‬8‫ٮ‬6‫ٮًﺎ ﻋ*ٮﺪ اﻟ*ٮﺴﺎء اﻟﻤﺴ*ٮﺎت اﻟﻼ‬.‫ ٮ "ﺤﺪث ﻫﺬا *ﻋﺎﻟ‬. ‫ٮًﺎ ﻋ‬,‫ﻋﺎﻟ‬/ ‫ڡرات‬6‫ا*ٮﻬ"ٮﺎر إﺣﺪى اﻟ*ڡ‬ Tendon: The forces of muscles in the body are transmitted by tendons. Tendons minimize the bulk at a joint. Tendons have to remain in their proper locations to function properly. The functions of patella: The patella also serves as a pulley for changing the direction of the force. Increase the mechanical advantage of the muscles that straighten the leg. Some of the greatest forces in the body occur at the patella. When a person is squatting, the tension in the tendons that pass over the patella may be more than two times his weight. :‫ﺮ‬$‫وٮ‬ ‫ﺤﺐ أن‬,5 ‫ ٮ‬.‫ڡﺼﻞ‬/‫ﺤﻢ اﻟﻤ‬,‫ڡﻠﻞ ﻣﻦ ﺣ‬$$‫ﺎر ٮ‬$‫ اﻷوٮ‬.‫ﺎر‬$‫ﺤﺴﻢ ﻋﻦ ﻃريﻖ اﻷوٮ‬,‫ڡوى ﻋﻀﻼت اﻟ‬$.‫ٮﺸكﻞ ﺻﺤيﺢ‬, ‫ٮﻌﻤﻞ‬$‫ٮﺔ ﻟ‬,‫ٮﺎﺳ‬/‫ڡﻌﻬﺎ اﻟﻤ‬$‫ى ﻣوا‬1‫ڡ‬/ ‫ﺎر‬$‫ڡﻰ اﻷوٮ‬$‫ٮ‬,$‫ٮ‬ :‫ڡﺔ‬/‫ﻃﺎﺋﻒ اﻟﺮﺿ‬/‫و‬.‫ڡﻮة‬$‫ﺤﺎه اﻟ‬,$‫ٮيﺮ اٮ‬5‫ﻌ‬U‫ٮ‬$‫ٮﻜﺮة ﻟ‬, ‫ٮﺔ‬,‫ٮﺎ‬c‫ٮﻤ‬, ‫ﻀﺎ‬ ً 5 ‫ڡﺔ أٮ‬/‫ﻌﻤﻞ اﻟﺮﺿ‬$‫ ٮ‬.‫ڡويﻢ اﻟﺴﺎق‬$‫ٮ‬$‫ٮ‬, ‫ڡﻮم‬$$‫ٮﺔ ﻟﻠﻌﻀﻼت اﻟﱵ ٮ‬5‫ٮﻜ‬5‫ٮ‬/‫ٮﲀ‬5‫ٮﺰة اﻟﻤ‬5‫ زيﺎدة اﻟﻤ‬ ‫ى وﺿﻊ‬1‫ڡ‬/ ‫ﺤﺺ‬/‫ﻜون اﻟﺸ‬5 ‫ٮﺪﻣﺎ ٮ‬/‫ ﻋ‬.‫ڡﺔ‬/‫ٮﺪ اﻟﺮﺿ‬/‫ﺤﺪث ﻋ‬$‫ﺤﺴﻢ ٮ‬,‫ى اﻟ‬1‫ڡ‬/ ‫ڡوى‬$‫ﻄﻢ اﻟ‬/‫ﺾ أﻋ‬ ‫ٮﺮ‬c‫ﻜون أﻛ‬5 ‫ڡﺪ ٮ‬$ ‫ڡﺔ‬/‫ڡوق اﻟﺮﺿ‬/ ‫ﻤﺮ‬$‫ﺎر اﻟﱵ ٮ‬$‫ى اﻷوٮ‬1‫ڡ‬/ ‫ﺮ‬$‫ٮﻮٮ‬$‫ڡﺈن اﻟ‬/ ،‫ڡﺼﺎء‬/‫ﺮ‬ 2. Frictional Forces: When a person is walking, a force is transmitted from the foot to the ground. We can resolve this force into: A. the vertical reaction force is supplied by the surface (normal force) N. B. the horizontal reaction component must be supplied by frictional forces. f = µN  ‫‪$.2‬ڡوى اﻻﺣ‪$‬ٮﲀك‪:‬‬ ‫ﻋ‪/‬ٮﺪﻣﺎ ٮ ‪5‬ﻤﴚ اﻟﺸ‪/‬ﺤﺺ‪ ،‬ٮ‪/$‬ٮ‪$‬ٮ‪$‬ڡﻞ اﻟ‪$‬ڡﻮة ﻣﻦ اﻟ‪$‬ڡﺪم إﻟﻰ اﻷرض‪.‬‬ ‫ٮ ‪5‬ﻤﻜ‪/‬ٮ‪/‬ٮﺎ ﺣﻞ ﻫﺬه اﻟ‪$‬ڡﻮة إﻟﻰ‪:‬‬ ‫أ‪.‬ٮ ‪$5‬ٮﻢ ٮ‪$‬ﻮ‪/‬ڡ‪5‬ٮﺮ ‪$‬ڡﻮة رد اﻟ‪/‬ڡﻌﻞ اﻟﻌﻤﻮدٮ ‪5‬ﺔ ﻣﻦ اﻟﺴﻄﺢ )اﻟ‪$‬ڡﻮة اﻟﻌﻤﻮدٮ ‪5‬ﺔ( ‪.N‬‬ ‫ب‪.‬ٮ ‪,5‬ﺤﺐ أن ٮ ‪$5‬ٮﻢ ٮ‪U$‬ﻌﺬٮ ‪5‬ﺔ ﻣﻜون اﻟ‪$‬ٮ‪/‬ڡﺎﻋﻞ اﻷ‪/‬ڡ‪$‬ڡ‪1‬ى ‪,‬ٮواﺳﻄﺔ ‪$‬ڡوى اﻻﺣ‪$‬ٮﲀك‪.‬‬ ‫‪µ: is the coefficient of friction between two surfaces.‬‬ ‫‪The horizontal force component is approximately 0.15W, where‬‬ ‫‪W is the person's weight. This frictional force is important to‬‬ ‫‪prevent the person from slipping.‬‬ ‫‪For a rubber heel on a dry concrete surface, f = W, (µ = 1),‬‬ ‫‪which is much larger than the needed horizontal force‬‬ ‫‪component (0.15W) to prevent a person from slipping. On an‬‬ ‫‪icy, wet oily surface, where µ < 0.15, a person is slipping.‬‬ ‫‪If there is a disease in the joint, the friction may become large.‬‬ ‫‪The synovial fluid in the joint is involved in the lubrication.‬‬ ‫‪Example, the saliva we add when we chew food acts as a‬‬ ‫‪lubricant.‬‬ ‫‪.‬ﻫﻮ ﻣﻌﺎﻣﻞ اﻻﺣ‪$‬ٮﲀك ‪,‬ٮيﻦ ﺳﻄﺤ‪5‬ٮﻦ ‪µ:‬‬ ‫ٮ ‪,5‬ٮﻠﻎ ﻣﻜون اﻟ‪$‬ڡﻮة اﻷ‪/‬ڡ‪$‬ڡ‪5‬ٮﺔ ﺣوال‪1‬ى ‪ 0.15‬واط‪ ،‬ﺣ‪5‬ٮﺚ ‪ W‬ﻫﻮ وزن اﻟﺸ‪/‬ﺤﺺ‪$.‬ڡﻮة‬ ‫اﻻﺣ‪$‬ٮﲀك ﻫﺬه ﻣﻬﻤﺔ ﻟﻤ‪/‬ٮﻊ اﻟﺸ‪/‬ﺤﺺ ﻣﻦ اﻻ‪/‬ٮزﻻق‪.‬‬ ‫‪,‬ٮﺎﻟ‪/‬ٮﺴ‪,‬ٮﺔ ﻟﻠﻜﻌﺐ اﻟﻤﻄﺎط‪1‬ى ﻋﲆ ﺳﻄﺢ ‪/‬ﺣﺮﺳﺎ‪/‬ٮ‪1‬ى ‪,‬ﺣﺎف‪ ،f = W، (µ = 1) ،‬وﻫﻮ‬ ‫أﻛ‪,‬ٮﺮ ‪,‬ٮﻜ‪c‬ٮ‪5‬ٮﺮ ﻣﻦ ﻣﻜون اﻟ‪$‬ڡﻮة اﻷ‪/‬ڡ‪$‬ڡ‪5‬ٮﺔ اﻟﻤﻄﻠو‪,‬ٮﺔ )‪ (0.15W‬ﻟﻤ‪/‬ٮﻊ اﻟﺸ‪/‬ﺤﺺ ﻣﻦ‬ ‫اﻻ‪/‬ٮزﻻق‪.‬ﻋﲆ ﺳﻄﺢ زيﱵ ‪,‬ﺣﻠ‪5‬ٮﺪي رﻃﺐ‪ ،‬ﺣ‪5‬ٮﺚ ‪ ،µ < 0.15‬ٮ ‪/5‬ٮﺰﻟﻖ اﻟﺸ‪/‬ﺤﺺ‪.‬‬ ‫إذا ﰷن ﻫ‪/‬ٮﺎك ﻣﺮض ‪/‬ڡ‪1‬ى اﻟﻤ‪/‬ڡﺼﻞ‪/ ،‬ڡﺈن اﻻﺣ‪$‬ٮﲀك ‪$‬ڡﺪ ٮ ‪5‬ﺼ‪,‬ٮﺢ ﻛ‪,‬ٮ‪5‬ٮرا‪.‬ويﺸﺎرك‬ ‫اﻟﺴﺎﺋﻞ اﻟﺰﻟ‪5‬ٮﲇ ‪/‬ڡ‪1‬ى اﻟﻤ‪/‬ڡﺼﻞ ‪/‬ڡ‪1‬ى ﻋﻤﻠ‪5‬ٮﺔ اﻟ‪$‬ٮﺸﺤ‪5‬ٮﻢ‪.‬ﻋﲆ ﺳ‪,‬ٮ‬ ‫ﻋﲆ ﺳ‪,‬ٮ‪5‬ٮﻞ اﻟﻤ‪c‬ٮﺎل‪ ،‬اﻟﻠﻌﺎب اﻟﺬي ‪/‬ٮﻀ‪5‬ٮ‪/‬ڡﻪ ﻋ‪/‬ٮﺪﻣﺎ ‪/‬ٮﻤﻀﻎ اﻟﻄﻌﺎم ٮ ‪5‬ﻌﻤﻞ ﻛﻤ‬ ‫ﻛﻤواد ٮ'ﺸﺤ‪+‬ٮ م‬  The intestines have a slow rhythmic motion as it move food toward its final destination. All of these organs are lubricated by slippery mucus covering to minimize friction ‫ٮﻪ‬$‫ﺣﻬ‬,‫ٮﺤﻮ و‬/ ‫ڡﻞ اﻟﻄﻌﺎم‬$‫ٮ‬/$‫ٮﺚ ٮ‬5‫ٮﺌﺔ ﺣ‬5‫ٮﻄ‬, ‫ٮﺔ‬5‫ڡﺎﻋ‬$5 ‫ٮﺤﺮﻛﺔ إٮ‬, ‫ٮﻊ اﻷﻣﻌﺎء‬$‫تﻤ‬$‫ٮ‬ ‫ﺤ‬/‫ﻌﻄﺎء ﻣ‬U‫ٮ‬, ‫ٮﻢ كﻞ ﻫﺬه اﻷﻋﻀﺎء‬5‫ﺸﺤ‬$‫ٮﻢ ٮ‬$5 ‫ ٮ‬.‫ٮﺔ‬5‫ٮﻬﺎﺋ‬/‫اﻟ‬ ‫ٮﻞ اﻻﺣ'ٮﲀك‬5‫ڡﻠ‬$‫ٮ‬$‫ى زﻟﻖ ﻟ‬1‫ﺤﺎط‬/‫ﻣ‬ 3. Dynamic Forces: These forces when acceleration or deceleration is involved. In cases where the acceleration or deceleration is constant, then the Newton's second law: F=ma :‫ٮﺔ‬5‫ٮﻜ‬5‫ٮﺎﻣ‬/5 ‫ڡوى اﻟﺪٮ‬$‫ اﻟ‬.3 m: mass ‫ٮﺴﺎر ع أو‬$‫ٮﺎﻟ‬, ‫ٮﻌﻠﻖ اﻷﻣﺮ‬$5 ‫ٮﺪﻣﺎ ٮ‬/‫ڡوى ﻋ‬$‫ﻫﺬه اﻟ‬ a: acceleration ‫ٮﺴﺎر ع‬$‫ٮهﺎ اﻟ‬5‫ڡ‬/ ‫ﻜون‬5 ‫ى اﻟﺤﺎﻻت اﻟﱵ ٮ‬1‫ڡ‬/.‫ٮﺎﻃﺆ‬,‫ٮ‬$‫اﻟ‬ since a :‫ى‬1‫ٮ‬/‫ٮﺎ‬c‫ﻦ اﻟ‬$‫ٮﻮٮ‬5‫ٮ‬/ ‫ٮون‬/‫ڡﺎ‬$ ‫ڡﺈن‬/ ،‫ٮﺎ‬$‫ٮ‬,‫ﺎ‬c‫ٮﺎﻃﺆ ٮ‬,‫ٮ‬$‫أو اﻟ‬ F= change of moment / short time interval F= (This force is important when the body is moving and hitting another body). Example of dynamic force in the body is apparently increases of weight when the heart beats (systole) are increased..( ‫ﺣر‬/‫ﺤﺴﻢ آ‬,‫ٮ‬, ‫ﺤﺴﻢ ويﺼﻄﺪم‬,‫ٮﺤﺮك اﻟ‬$5 ‫ٮﺪﻣﺎ ٮ‬/‫ڡﻮة ﻣﻬﻤﺔ ﻋ‬$‫)ﻫﺬه اﻟ‬ ‫ٮﺪ زيﺎدة‬/‫ٮﺪو زيﺎدة اﻟوزن ﻋ‬,5 ‫ﺤﺴﻢ ﻋﲆ ﻣﺎ ٮ‬,‫ى اﻟ‬1‫ڡ‬/ ‫ٮﺔ‬5‫ٮﻜ‬5‫ٮﺎﻣ‬/5 ‫ڡﻮة اﻟﺪٮ‬$‫ٮﻠﺔ اﻟ‬c‫وﻣﻦ أﻣ‬ ‫ڡﻠﺐ‬$‫ٮﻀﺎت اﻟ‬,‫ٮ‬/ ‫ٮٮ‬/ Safety devices of cars: Headrest. Seat belts. Shoulder belts. Air bag. Penetration – resistance windshields. Side door beams. Energy absorbing steering column. It reduces the decelerative forces during a collision by increasing the time the trunk of the body takes to come to a stop. :‫ٮﺎرات‬5‫ٮﺎﻟﺴ‬, ‫ﺣﻬﺰة اﻟﺴﻼﻣﺔ‬,‫أ‬.‫ٮﺪ اﻟرأس‬/‫ ﻣﺴ‬.‫ ﺣزام اﻻﻣﺎن‬.‫ٮﻒ‬$‫ أﺣﺰﻣﺔ اﻟﻜ‬.‫ٮﺔ‬5‫ وﺳﺎدة ﻫواﺋ‬.‫ڡﺎوم‬$‫ى اﻟﻤ‬1‫ﺣﺎج اﻷﻣﺎم‬,‫ٮراق – اﻟﺰ‬$‫ﺣ‬/‫ اﻻ‬.‫ٮواب‬,‫ٮﺔ ﻟﻸ‬5‫ٮ‬,‫ٮ‬/‫ﺣﺎ‬, ‫ ﻋوارض‬.‫ڡﺔ‬$‫ٮﺺ ﻟﻠﻄﺎ‬$‫ٮﻪ ﻣﻤ‬5‫ﺣ‬,‫ﻮ‬$‫ ﻋﻤﻮد ٮ‬ ‫ڡﺖ‬$‫ٮﺎء اﻻﺻﻄﺪام ﻋﻦ ﻃريﻖ زيﺎدة اﻟﻮ‬/c‫ٮﺎﻃﺆ أٮ‬,‫ٮ‬$‫ڡوى اﻟ‬$ ‫ڡﻠﻞ ﻣﻦ‬$5 ‫ڡﻬﻮ ٮ‬/ ‫ﺤﺴﻢ ﻟ ٮ"ﻮ"ڡف‬,‫ﺣﺬع اﻟ‬, ‫ڡﻪ‬$‫ﻌﺮ‬U‫ٮ‬$‫ﺴ‬5 ‫اﻟﺬي ٮ‬ Fatima Riyadh