23、電腦的外殼是以鎂鋁合金製造，此材料是屬於： (A)有機質材料 (B)無機質材料 (C)鐵金屬材料 (D)非鐵金屬材料。

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。