حلول التدريبات العملية الطاقة بالجاذبية

5. ب.1- سرعة الاصطدام لجسم يُلقى لأسفل.

أثناء حركة الجسم، فقط قوة الجاذبية هي التي تنجز شغلًا، لذلك يتحقق قانون حفظ الطاقة الميكانيكية. 

نكتب معادلة حفظ الطاقة، ونستخدم تعبير طاقة وضع الجاذبية.

نقارن الطاقة الميكانيكية في النقطة A بالطاقة الميكانيكية في النقطة B ونعبر عن سرعة الجسم في النقطة B:

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نكتب معادلة الطاقة بطريقة مفصّلة، ونعبر منهاعن سرعة الجسم في اللحظة التي يصيب فيها الأرض (V_B). 

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