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本刊2001第12期和2002第11期《判定杠杆平衡问题的一个通式》及《补充》中,分别介绍了涉及浮力的杠杆平衡问题的通式1-(ρ_液/ρ_物)和1-n·(ρ_液/ρ物).笔者认为,用这个简单结论去解决类似的问题,的确是一种既省时又省事的好方法,但其推理过程复杂,且不易掌握,学生一旦忘记结论,将会束手无策.这里我跟大家介绍一种判定杠杆平衡问题的通用方法——扩大、假设法.下面举例说明这一方法的具体应用.杠杆平衡问题可以分为以下几种情况:
In 2001 and No. 12 of 2002 and No. 11 of 2002, “One Formula for Judging the Problem of Lever Balance” and “Supplement”, the general formula 1-(ρ_liquid/ρ_material) concerning the balance of buoyancy was introduced respectively. And 1-n·(ρ_liquid/p-material). The author believes that using this simple conclusion to solve similar problems is indeed a good way to save time and save trouble, but its reasoning process is complex and difficult to grasp. Once students forget the conclusions, they will be at a loss. Here I will introduce a general method to determine the balance of leverage - expansion, hypothesis. The following examples illustrate the specific application of this method. Lever balance can be divided into the following situations :