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在物理习题中常见一些题目,其已知条件和待求的结论常常处于隐蔽状态。求解这类题,关键在于挖掘这些隐蔽条件。本文试以初中物理习题为例,谈谈挖掘习题中隐蔽条件的几种途径。 1 从物理概念的内涵挖掘隐蔽条件 物理概念是求解物理习题最基本的依据之一。不少物理题的部分条件隐含在相关的概念中。解题时可以从概念的内涵挖掘隐蔽条件。 [例1]如图1所示,O是杠杆的支点,AB=2OA,G=15牛。当一动力F作用在B点时,恰能使杠杆处于平衡状态,求力F′的大小。 析与解:由题中的“平衡状态”这一概念的内涵可知,杠杆所受动力F、阻力F′,动力臂OE、阻力臂OA符合下列关系:
Some common problems in physics exercises, their known conditions and pending conclusions are often hidden. The key to solving such questions lies in mining these hidden conditions. This article tries to use junior high school physics exercises as an example to talk about several ways of mining concealed conditions in the exercises. 1 Mining hidden conditions from the connotation of the physical concept The physical concept is one of the most basic basis for solving physical exercises. Some of the conditions for many physical problems are implicit in the relevant concepts. When solving a problem, you can discover hidden conditions from the connotation of the concept. [Example 1] As shown in Fig. 1, O is the fulcrum of the lever, AB=2OA, G=15N. When a force F acts on point B, the lever can be balanced and the force F’ can be found. Analysis and reconciliation: From the meaning of the concept of “balanced state” in the title, it can be seen that the power F, resistance F′, power arm OE, and resistance arm OA of the lever meet the following relationships: