题目

已知物体在倾角为α的斜面上恰能匀速下滑，则物体与斜面间的动摩擦因数是；如果物体质量为m ， 当对物体施加一个沿着斜面向上的推力时恰能匀速上滑，则这个推力大小是． 答案：【1】tanα【2】2mgsinα What they need ______ enough money, while what we need ______ enough workers. A. is; is             B. are; are     C. is; are           D. are; is