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一般书上的视重、失重与超重等概念都缺乏明确的定义和清楚的解释,使学生在理解上感到困难。本文试从定义和联系物体内部的相互作用来理解这两个方面提出一些看法。一、视重应定义为“物体与支持物相对静止并不受地球、支持物以外其它作用时,物体对支持物的作用力。”从此出发,可明确以下几点: 1.地面上物体的视重。表现为相对地面静止对弹簧秤测得的重量G,大小和方向等于地面上观察者观察到的重力加速度g和物体质量m的乘积G=mg。由于地球上的物体随地球自转做圆周运动,所需向心力ma_c为所受地球引力ma(a=(GM)/R~2)与支持力N的合力,物体的视重G为N的反作用力,因此,mg=ma-ma_c。
Concepts such as weight, weightlessness, and overweight in the general book lack clear definitions and clear explanations, which make students feel difficult to understand. This article attempts to provide some perspectives on the understanding of these two aspects from the definition and the interaction within the object. First, the visual weight should be defined as “The relative force of the object and the support is not affected by anything other than the earth or the support. The force of the object on the support.” From this point of departure, the following points can be made clear: 1. On the ground The weight of the object. Shown as relative to the ground static weight measured on the spring balance G, size and direction equal to the observer observed on the ground gravitational acceleration g and the mass m of the product of the product G = mg. Since the earth’s objects move in a circular motion with the earth’s rotation, the required centripetal force ma_c is the combined force of the Earth’s gravitational force ma (a=(GM)/R~2) and support force N. The object’s apparent weight G is the reaction force of N. Therefore, mg=ma-ma_c.