ELI5: Explain Like I'm 5

Theorem of three moments

Okay, imagine you have a really long, thin rod that's standing up straight. This rod is being supported by two points at each end, like someone holds a pencil by pinching it between their thumb and pointer finger.

Now, let's say you want to put some weight on the rod, like a book or a block. If you put that weight right in the middle of the rod, it might not be too hard for the rod to keep standing upright. But what if you put the weight closer to one end?

Well, the closer you put the weight to one end, the harder it's going to be for the rod to stay standing. And if you put too much weight too close to one end, the rod might just topple over on that side.

This is where the theorem of three moments comes in. The theorem helps us understand how much weight we can put on the rod before it falls over.

To use the theorem, we need to know three things: the weight of the object we're putting on the rod, how far away from the center of the rod we're putting the weight, and how long the rod is.

Based on these three things, we can calculate three different "moments" (which are basically just ways of measuring how hard the weight is pulling on the rod). Then we can use those moments to see how much the rod is bending or flexing, and figure out whether it's going to stay standing or fall over.

By using the theorem of three moments, we can make sure that we're not putting too much weight on the rod, or putting it in the wrong place, and prevent it from falling over.