中学物理内容繁多,其重要部分力学首当其冲。而对物体作受力分析是这一部分的基础。对于常见的三种力:重力、弹力、摩擦力,在具体问题的分析中,关键在于这些力的方向的确定。但这恰好是中学生常易犯错误的地方。 为扭转对力学这一部分问题感到棘手的被动局面,我们采用逐步过渡的教学方法。 首先让同学们明确这三种力的产生条件。我们利用日常见到的例子(比比皆是),反复强调加以说明。重力是地球上、地球引力范围内都会受到的一种力,由于地球对物体的吸引力而产生。弹力产生的条件是物体之间互相接触、且有挤压,有接触而无挤压的二个物体间不会存在弹力。因弹力的产生以物体产生弹性形变为基础。摩擦力因涉及静摩擦力与滑动摩擦力可分开说明。但总的来说,只要两物体互相接触的表面有相对运动或相对运动趋势即可存在。讲摩擦力必须对相对运动的含意讲述清楚,相对两字是个重 There are many physics in middle school, bear the brunt of the important part of mechanics. The force analysis of objects is the basis of this part. For the three common forces: gravity, elasticity, friction, in the analysis of specific problems, the key lies in the determination of the direction of these forces. But this happens to be a common mistake for middle school students. In order to reverse the thorny and passive situation on the part of mechanics, we adopt a gradual transitional teaching method. First of all, let the students clarify the conditions for the emergence of these three forces. We use the daily examples (abound), repeatedly stressed to explain. Gravity is a force on Earth, within the gravitational sphere of the Earth, generated by the Earth’s attraction to objects. Elastic force is generated by the objects in contact with each other, and there is extrusion, there is contact without squeezing between the two objects will not exist elastic. Due to the generation of elastic objects to produce elastic deformation-based. Friction can be described separately as it relates to static friction and sliding friction. However, as a general rule, there is a relative or relative tendency of the two objects to contact one another. Speaking of friction must be clear about the meaning of the relative movement, relative to the word is a weight