17、噴流水柱之直徑與其源頭出口直徑相比，符合下列哪一敘述？ (A) 相等 (B) 較大 (C) 較小 (D) 不一定。

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。