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一些力学问题的研究对象牵涉两个或多个物体若题目不要求讨论研究对象中各物体的受力及运动情况,只要求讨论研究对象整体的
Some subjects of mechanical problems involve two or more objects. If the topic does not require the discussion of the force and movement of each object in the study object, only the entire subject must be discussed.