Page 269 - statbility for masters and mates

Second moments of areas 257
Fig. 29.2
b=2 b=2
b=2 x3 b=2
l 3 b=2 IAB lb3
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To ®nd the second moment of a rectangle about one of its sides. Consider the second moment (i) of the elementary strip shown in Figure
IAB IAB l
lx2 dx b=2
x2 dx
29.3 about the axis AB.
Let IAB be the second moment of the rectangle about the axis AB, then:
i lEdx x2
b O
lx2 dx x3 b
IAB l3O