38.圖(十一)之複合結構中,BD 桿件所受到之軸張力約為多少kgf? (A) 18 kgf  (B) 28 kgf (C) 47 kgf (D) 61 kgf

39. 圖(十二)中a、b、c桿件之材料彈性模數(Elastic Modulus)為E、斷面積為A, a、c 桿件長度為b桿件的二倍,則a、b、c三根桿件所受到的拉力分別為:(A) a 桿拉力=P、b 桿拉力=P、c 桿拉力=P(B) a 桿拉力=\(\frac{P}{3}\)、b 桿拉力=\(\frac{P}{3}\)、c 桿拉力=\(\frac{P}{3}\)(C) a 桿拉力=\(\frac{P}{4}\)、b 桿拉力=\(\frac{P}{2}\)、c 桿拉力=\(\frac{P}{4}\)(D) a 桿拉力=\(\frac{2P}{5}\)、b 桿拉力=\(\frac{P}{5}\)、c 桿拉力=\(\frac{2P}{5}\)