複選題52、 At which angle of a crystal direction to the applied load may a slip along it not take place? (A) 30° (B) 45° (C) 60° (D) 90°

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。