1、請計算 A、B 兩處的作用力，當α角為 30∘時？ (A) A=165N; B=165N (B) A=430N; B=275N (C) A=219N; B=141.5N (D) A=275N; B=430N。

10、 In Figure 10, a horizontal force of 500 N acts on a block of weight 1.5 kN placed on an inclined plane. The coefficients of friction between the block and the plane are μs =0.25 andμk = 0.20 . What is the actual frictional force? (A) 200N (B) 500 N (C) 300 N (D) 450 N。