3. قوة تعمل بزاوية
3.2. التوتربالخيط الواصل بين جسمين على سطح أفقي غير أملس
نستخدم المعادلة التي طوّرناها بالبند السابق ونعوّض فيه التسارع الذي وجدناه :
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