关山难越,____? ____,尽是他乡之客。
如图所示,在光滑的水平面上叠放着M,P,N三个物体,质量分别为m,2m和m,M,N,P间动摩擦因数均为μ,系统处于静止状态,现对P施加一个水平向右的拉力F,欲使P从M和N中拉出来,则F必须大于( )
— Mom, I was the first to reach the top of the mountain.— Good job, Charlie. I'm ______ of you.