用细丝线拉动线轴状刚体在水平平面桌面上( 或水平导轨上) 的运动，是典型的平面平行运动. 改变细丝线拉力的 倾角或方式，线轴状刚体可以有多种不同的运动状态，因此这是一个有趣的演示实验. 之所以线轴状刚体有多种运动状态，关 键因素是线轴状刚体在作纯滚动时它与平面桌面或导轨之间的相互作用力是静摩擦力，静摩擦力可以在一定范围连续变化 以使线轴状刚体的运动能够满足动力学方程和运动学方程. 当所需要的静摩擦力超出其最大允许值时，线轴状刚体与平面桌 或导轨之间将出现滑动，二者之间的摩擦力将由静摩擦力变为滑动摩擦力，纯滚动状态将消失.

As the spool - like rigid body is driven by the filament，its movement on the horizontal plane table ( or the horizontal rail) is a typical plane parallel motion. To change the inclination or way of the filament tension，the spool - like rigid body can present different motion states，which is an interesting demonstration experiment. The reason why the biaxial rigid body presents different motion states，the key factor is that the static friction dominates as the rigid body rolls on the desktop or the rail. The static friction can continuously vary in some ranges，so the linear movement of the rigid body can satisfy the kinetic equation and the kinematics equation. As the required staticfriction exceeds the maximum value，the spool - like rigid body will slide on the table. Also，the friction will change from the static friction to the sliding friction，and the pure rolling state will disappear.