一、本月知识学习指要力可使物体发生形变，也可使物体的运动状态发生改变．三种力（重力、弹力和摩擦力）的产生机理是不同的．要注意线绳形变产生的拉力沿着线绳的收缩方向，面与面、点与面接触处的弹力垂直于接触面（若为曲面则垂直于切面），点与杆接触处的弹力垂直于杆． First, this month’s knowledge learning refers to the ability to deform objects, but also to change the movement of objects. The mechanism of the three forces (gravity, elasticity, and friction) is different. Pay attention to the tension generated by the deformation of the wire rope along the direction of contraction of the wire. The elastic force at the contact between the surface and the surface, point and surface is perpendicular to the contact surface (if the surface is perpendicular to the cutting surface), the elastic force at the contact point of the wire and the rod is perpendicular to the Pole.