Class 12 Tensegrities
PROFESSOR: Alright, lecture 12 is about tensegrities, like this one which you saw. And when they're rigid-- infinitesimal rigidity, and carpenter's rule theorem, all in one quick lecture. So, just a couple questions about tensegrities. Well first is about infinitesimal rigidity in general. This is sort of extra, bonus. I talked about one reason why this dot product condition is the right thing, which is based on projection. But there are other ways to think about it. So let's say we have an edge, vw-- actually I think I'll draw it w on the left. So here's vw. We would think of this point is being c of w, that's your configuration. This point is c of e. Then we were talking about when, if you have a velocity vector, d of w, and a velocity vector-- Say something like this, d of v, when it preserves the length of this bar to the first order. And the condition we had was c of v minus c of w dot product with d of v minus d of w equals 0. So the question...