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在复习力与运动这个知识板块的过程中,很多教师都会从下面这道例题来构建整个知识结构,并进行拓展延伸.例题如图1所示,一块重为10 N的正方体物块A,放在水平桌面上,桌面右端固定一定滑轮,一个轻质小盘通过一个细线绕过定滑轮和物体A相连,当轻质小盘中挂0.2 kg的砝码时(小盘重忽略不计),物体A处于静止状态,此时物体A的受摩擦,摩擦力大小是,当小盘中砝码质量增加到0.3 kg时,物体A做匀速直线运动,此时物体A受摩擦,摩擦力大小是,如果将小盘中砝码的质量增加到0.4 kg时,物体A将会做运动,此时的摩擦力大小是,若
In the process of reviewing the knowledge and movement of the knowledge section, many teachers will build the entire knowledge structure from the following example and expand and extend the example. As shown in Figure 1, a square block A with a weight of 10 N is placed. On the horizontal table top, a certain pulley is fixed on the right side of the desktop, a light small plate is connected with the object A through a thin line around the fixed pulley, when hanging a weight of 0.2 kg in the small light plate (small disc weight is ignored), The object A is in a static state. At this time, the friction and friction force of the object A is. When the weight of the small disk increases to 0.3 kg, the object A performs a straight-line linear motion. At this time, the object A is subject to friction, and the friction force is If the mass of the weight in the small disk is increased to 0.4 kg, the object A will move. At this time, the friction force is