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摩擦力的概念既是进行物体受力分析的重点,又是力学计算的难点和关键,但一些学生由于弄不清静摩擦力与动摩擦力的联系与区别,常误认为两种摩擦力总是阻碍物体运动的;两种摩擦力的大小都跟正压力成正比;任何两个相互接触并保持相对静止的物体之间一定存在静摩擦力等。针对以上问题,在教学中应重点讲清以下几方面。一、正确判断有无摩擦力要正确无误地判断是否有摩擦力存在,关键是掌握和理解摩擦力产生的三个条件:1接触面粗糙,即μ不等于0;2接触面上发
The concept of friction is not only the focus of stress analysis of objects, but also the difficulty and key of mechanical calculation. However, some students mistakenly think that the two kinds of friction always obstruct the object because they can not understand the relationship between static friction and dynamic friction Exercise; the size of both types of friction is proportional to the positive pressure; there must be static friction between any two objects that are in contact with each other and remain relatively stationary. In response to the above problems, teaching should focus on the following aspects. First, the correct judgments with or without friction To correctly determine whether there is friction exists, the key is to grasp and understand the friction generated by the three conditions: 1 contact surface roughness, that μ is not equal to 0; 2 contact surface hair