Stability and moment of inertia

[Jason03]

The problem and my work is below...I believe I got the problem to work out. The only question I had was if I found the LEAST moment of inertia which is what's needed for the formula at the end of my calculations. What exactly is meant by the least moment of inertia?

http://i674.photobucket.com/albums/vv106/jason03_2009/prob7-1.jpg

http://i674.photobucket.com/albums/vv106/jason03_2009/prob7-2.jpg

 

[PhanthomJay]

The problem and my work is below...I believe I got the problem to work out. The only question I had was if I found the LEAST moment of inertia which is what's needed for the formula at the end of my calculations. What exactly is meant by the least moment of inertia?

You have calculated the least (minor axis) moment of inertia by assuming the 4 feet as your 'b' and 2 feet as your 'h'. The major axis moment of inertia is much greater ( using 2 feet as the 'b' and 4 feet as the 'h'); hence, the wall is much less stable along the weak axis, and thus, the least moment of inertia applies.

 

[Jason03]

ok I see... so if the rectangle was rotated than the major axis would be calculated with the base being 2 and height being 4.