题目

10只相同的轮子并排水平排列，圆心分别为O1、O2、O3…、O10，已知O1O10=3.6m，水平转轴通过圆心，轮子均绕轴以n=r/s的转速顺时针转动．现将一根长L=0.8m、质量为m=2.0kg 的匀质木板平放在这些轮子的左端，木板左端恰好与O1竖直对齐（如图所示），木板与轮缘间的动摩擦因数为μ=0.16．则木板水平移动的总时间为（    ）                                                                                           —Will we have dinner at the Hope Restaurant?—Maybe.We'll go there if the show ______ before 6.But I don't know if there ______ any free tables then.A. will end，were B. will end，will beC. ends，were D. ends，will be