複選題49、在下列金屬中，晶體結構之配位數(coordination number)為 12 者，是： (A) Ag (B) Mo (C) α -Ti (D) Cr

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。