The top section is a rectangle with width $b_1 = 40 mm$ and height $h_1 = 25 mm$. Its moment of inertia about its centroidal axis is:
$I_1 = \frac{1}{12}b_1h_1^3 = \frac{1}{12}(40)(25)^3 = 52083.33 mm^4$
The bottom section is a rectangle with width $b_2 = 30 mm$
Show more…