Question:-
A beam cross-section is used in two different orientation as shown I the figure given below

Bending moments applied to the beam in both case are same. The maximum bending stresses induced in cases (A) and (B) are related as
Option (A)
sA = sB
Option (B)
sA = 2sB
Option(C)
sA = sB/2
Option(D)
sA = sB/4
Correct Option:
(B)
Question Solution:
For first case
lA = (1/12)xbx(b/2)3 = (b4/(12x8))
(M/lA)=(s/y) => ((Mx12x8)/b2) = (s/(b/4))
\ sA = (24M/b3)
For second case
lB = (1/12)x(b/2) x (b)3 = (b4/(12x2))
\ {M/(b4/(12x2))} = (sB/(b/2))
\ sB = (12M/b3)
\ sA = 2sB
question-answer-faq-5149