摩擦力是一个难点知识,有些同学很难掌握它。然而经常要分析匀速直线运动中的摩擦力,不能理解它的实质,只凭主观意识判断,往往又会出现错误。为了帮助同学们有效掌握这方面知识,现把这类题型介绍如下:题目用弹簧测力计沿水平方向拉着一木块,在水平木板上以2m/s的速度做匀速直线运动时,弹簧测力计的示数为2N,则木块受到的滑动摩擦力的大小为()A.3NB.2N Friction is a difficult knowledge, some students have a hard time grasping it. However, it is often necessary to analyze the friction in a uniform linear motion. It is not possible to understand the essence of it, and subjective judgment alone often leads to errors. In order to help the students to effectively grasp this knowledge, these types of questions are now described as follows: The subject is using a spring dynamometer to pull a block in the horizontal direction, and on a horizontal board at a speed of 2m/s for uniform linear motion. The number of spring dynamometers is 2N, then the sliding friction force of the wooden block is () A.3NB.2N