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指导学生利用超重和失重知识分析有关的力学问题,会使物理概念十分清晰,问题变得很简单,有利于培养学生分析问题和解决问题的能力. 一、超重和失重的概念质量为m的物体以竖直向上的加速度a运动时,它对水平支持面的压力N(或对竖直悬线的张力T)大于物体的重量,等于m(g+a).这种现象叫物体超重.常说物体超重了ma同理,物体以竖直向下的加速度a运动时,上述压力N(或张力T)等于m(g-a).这种现象叫物体失重,常说物体失重了ma.如果a=g则压力N(或张力T)为零,我们说物体完全失重. 例如,在绕地球作匀速圆周运动的卫星中的物体,由于它竖直向下的加速度a就是卫星所在位置的重力加速度g,所以该物体对卫星底板的压力为零,处于完全失重状态.
Instruct students to use the knowledge of overweight and weightlessness to analyze the relevant mechanical problems, make the physical concept very clear, the problem becomes simple, and help students develop the ability to analyze problems and solve problems. First, the concept of weight and weightless objects of mass m When moving with vertical acceleration a, its pressure on the horizontal support surface N (or the tension T on the vertical suspension line) is greater than the weight of the object, which is equal to m (g+a). This phenomenon is called the object is overweight. Saying that the object is overweight is the same as that of ma. When the object is moving with a vertical downward acceleration a, the above pressure N (or tension T) is equal to m(ga). This phenomenon is called weightlessness of the object. It is often said that the object has lost weight. ma =g pressure N (or tension T) is zero, we say that the object is completely weightless. For example, an object in a satellite orbiting the Earth at a constant speed due to its vertical acceleration a is the gravity acceleration of the satellite g, so the pressure of the object on the satellite floor is zero and it is in a state of total weightlessness.