摩擦力的有无及方向的判断,可根据摩擦力产生的条件进行判断,若两接触的物体间有弹力,接触面粗糙,两物体间有相对运动或有相对运动趋势时,在它们的接触面上就产生阻碍相对运动或相对运动趋势的力,这就是摩擦力。但在实际问题中,特别是当两物体间具有相同的速度时,摩擦力有无及方向的判断,学生有些困难,下面我们就以物块与传送带类型 The judgment of the presence or absence of friction and the judgment of the direction can be made based on the conditions under which the friction force is generated. If there is an elastic force between the two objects in contact and the contact surface is rough, there is a relative movement or relative movement tendency between the two objects, The face on the face of obstruction of relative movement or relative movement tendency of the force, which is the friction. However, in practical problems, especially when the two objects have the same speed, the presence of friction and the direction of judgment, the students have some difficulties, here we will block and conveyor type