A.Castles' structure and the eating habit in them. B.Castles' structure and the people who lived in them. C.Castles' structure and the life in them. D.Why people built castles and their structure.
【简答题】已知一质量 m =1 kg的物体在倾角 α =37°的斜面上恰能匀速下滑,当对该物体施加一个沿斜面向上的推力 F 时,物体恰能匀速上滑。(取 g =10 m/s 2 ,sin 37°=0.6,cos 37°=0.8) (1) 物体与斜面间的动摩擦因数 μ 是多大? (2) 求推力 F 的大小。