قالب:صورة اليوم المختارة/2019-09-21
![رقاص نيوتن، وهو نظامٌ يُوضحُ مفهومًا أساسيًّا في الميكانيكا الكلاسيكيَّة يتمثل في مبدأ حفظ زخم الحركة والطاقة](https://upload.wikimedia.org/wikipedia/commons/thumb/e/e8/Newtons_cradle_animation_book.gif/330px-Newtons_cradle_animation_book.gif)
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