設(shè)圖(a)、(b)所示兩根圓截面梁的直徑分別為d和2d,許可荷載分別為[P]1和[P]2。若二梁的材料相同,則[P]2/[P]1等于:()
A.2 B.4 C.8 D.16
(2006)如圖所示,直桿受扭轉(zhuǎn)力偶作用,在截面1—1和2—2處的扭矩為:()
A.5kN·m,5kN·m B.25kN·m,-5kN·m C.35kN·m,-5kN·m D.-25kN·m,25kN·m
A.2τ B.4τ C.8τ D.16τ