What are moments of inertia actually measuring?

[scottymo]

Hey there,

In my statics class we're just finishing up moments of area or moments of inertia as they're being called. I can do the math and figure them out just fine but I have no clue what I'm actually finding! What is it? I am having trouble actually conceptualizing what it is that I'm calculating. If anyone can explain or point me to a good explanation/video it would be greatly appreciated. I hate just calculating things when I don't know what for.

-Scott

 

[SteamKing]

There are two moments of area which are commonly used in science and engineering.

The first moment of area is used to find the centroid, or center or gravity, of a given figure or shape.

The second moment of area, often referred to as the moment of inertia, is used often in mechanics to calculate the bending stress in beams, or to compare the strength of two or more beams with given cross section shapes.

There are other uses for these quantities, but these two are some of the most commonly encountered.