一道AP 2012 力学题

一道AP 2012 力学题
A ring of mass M,radius R,and rotational inertia MR2 is initially sliding on a frictionless surface at constant velocity u0 to the right,as shown above.At time t = 0 it encounters a surface with coefficient of friction μ and begins sliding and rotating.After traveling a distance L,the ring begins rolling without sliding.Express all answers to the following in terms of M,R,u0 ,μ,and fundamental constants,as appropriate.
一个质量M,半径R,转动惯量为MR2（平方）的环开始在光滑水平面上以初速度V0向右滑动,t=0时刻进入滑动摩擦系数为μ的平面开始滑动同时滚动.经过L距离后环只滚动不滑动.
求：（1）线速度V与t关系式；（2）角速度w与t的关系式；（3）运动距离L所用时间；（4）L的大小.