即                                                                               

故                                                                    

小物块由最高点回到D点历时                      

小物块由C上升到最高点历时                                   

由机械能守恒知

物块沿斜面下滑：                       

所以

   （3）物块沿斜面上滑：                 

由牛顿第三定律知对轨道的压力为                                   

在O点                                                                   

所以N=43N