# When can you apply Ehrenfest's theorem?

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1. Oct 3, 2014

### Logan Rudd

I know when the initial state ($\Psi(x,0)$) is given, $\frac{d<x>}{dt} \not=<p>$. I thought you can only apply Ehrenfest's theorem when $\Psi$ is a function of x and t, however it seems like you can also apply it to the time-independent part ($\psi(x)$) by itself as well. Can someone explain to me why Ehrenfest's theorem is valid for $\psi(x)$?

Thanks!

Last edited by a moderator: Oct 4, 2014
2. Oct 3, 2014