There was a question on an exam I took earlier this year which gave a radial potential of the form V(r) = -A/r. In the first part of the question it asked what the uncertainty in x was (i.e. was is Δx?) In my notes I have: Δx = r since <x> = 0. I don't remember what verbal explanation went along with this so I'm confused how this conclusion was reached. Can someone help explain this to me. I feel like this is something really simple that I'm just overlooking. I know that from what's above that <x^2> should be r^2 since Δx = √(<x^2> - <x>^2).