حلول التدريبات العملية ديناميكا لجسم واحد
5. يتحرك جسم على سطح مائل غير أملس
5.4. التسارع تحت تأثير قوة خارجية باتجاه الطح المائل نحو الأسفل والاحتكاك
للتعبير عن مقدار تسارع جسم يتحرك لأسفل سطح مائل غير أملس، نرسم مخططًا للقوى ونكتب معادلات الحركة:
تعمل أربع قوى على الجسم: القوة الخارجية الأفقية F، قوة الاحتكاك، قوة الجاذبية والقوة العمودية:
نرسم مخطط القوى:

نحدد محور X في اتجاه نحو أسفل السطح المائل والمحور Y في اتجاه عمودي على المستوى.
نقوم بتحليل قوة الجاذبية W لمركبيها:
زاوية ميل السطح المائل هي الزاوية بين قوة الجاذبية W ومركّب قوة الجاذبية WX.

في الاتجاه العمودي للسطح الجسم في وضع اتّزان، نكتب معادلات الحركة في اتجاه المحور :Y
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في اتجاه نحو أسفل السطح المائل لا يستمر الجسم في حركته، بل يتحرك بتسارع. نكتب معادلات الحركة في اتجاه المحور:X
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نعوض تعبير القوة العمودية من معادلة الحركة في اتجاه المحور Y في معادلة الحركة في اتجاه المحور X:
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نعبّر عن التسارع:
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