Recent content by renec112

The physics of how to cool down your cup of coffee or tea fastest. Sponsored by Brilliant: https://brilliant.org/HiggsinoPhysics Stirring vs blowing vs cooli...

Physics challenges. 5 Popular questions answered.

How a superconductor works. Everything from the physics and some of the history as well.

Entropy and the thermodynamics second law dictates what direction heat flows. Why does heat flow from warm to cold and not the other way

The speed of light and black holes. What happens when at the speed of light? What about a black hole? This video explains how time dilations works.

Oh right.. I think i misunderstood the question then. I need to find ##< x(t)> ## for all later times. But i can't see, how i can find that.. You are saying ##\frac{d<x>}{dt} \neq < x(t)> ## I am not sure why i should fine ##< x >## I can see it's a part of the equation, but why does it give...

Thanks for helping me :) Its ##p = mv## off course. Oh i so the m' cancels and i am left with only ##<x>##... Nice trick ! Thank you :)

## v = \frac{1}{2} m v^2## ## = \frac{m^2v^2}{2m}## ## = \frac{p^2}{2m}## ## \Rightarrow p = \sqrt{2 v m}## Like this?

Oh I see. That's very smart. This is what i did: ##\frac{d<x>}{dt} = \frac{i}{\hbar} <[H,x]>## insert hamilton ##= \frac{i}{\hbar} <[P^2/2m,x]>## ##= \frac{i}{2 m \hbar } <[PP,x]>## ##= \frac{i}{2 m \hbar } <P[P,x]+[P,x]P>## ##= \frac{i}{2 m \hbar } <-P[x,P]-[x,P]P>## ##= \frac{i}{2 m \hbar }...

Actually when you say it like that.. I guess i thought in ## H = \frac{p^2}{2m} = \frac{\hbar}{2m}\frac{\partial^2}{\partial x^2}## the ##p## is just a constant but off course it's an operator: ##p = i \hbar \frac{\partial}{\partial x}## I guess the only thing to do is to differentiate a couple...

Hello physics forums. I'm trying to solve an old exam question. Would love your help. Homework Statement A free particle in one dimension is described by: ## H = \frac{p^2}{2m} = \frac{\hbar}{2m}\frac{\partial^2}{\partial x^2}## at ##t = 0## The wavefunction is described by: ## \Psi(x,0) =...

Okay i think i understand so we are calculating: ##\sigma_x \sigma_{L_x} \geq |\frac{1}{2i} <[x,L_x]>| ## and not: ##\sigma_x \sigma_{L_z} \geq |\frac{1}{2i} <[x,L_z]>| ##? Thank you for helping me.

Me and my group had a laugh at this, we are just finished doing it and it was very nasty indeed :D Thank you very much for the comment. - You mean ## <\sigma_{L_z}^2> ## and not ## <\sigma_{L_x}^2> ## Right? We have actually calculated ##<L_z## and ##<L_z^2>## from another task. We did it...

Hi physics forms! I'm practicing to for an Quantum mechanics exam, and i have a problem. 1. Homework Statement I have two problems, but it's all related to the same main task. I have a state for the Hydrogen: ## \Psi = \frac{1}{\sqrt{2}}(\psi_{100} + i \psi_{211})## where ## \psi_{nlm}##...

Off course! Thanks for being so patient with me. Now it works out :)