Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Quantum mechanics, expectation value

  1. Oct 25, 2011 #1


    User Avatar
    Gold Member

    1. The problem statement, all variables and given/known data
    Show that for the expectation values the following relations hold: [itex]d \langle x \rangle /dt =\langle p \rangle /m[/itex] and [itex]d \langle p \rangle /dt = - \langle d V/dx \rangle[/itex].

    2. Relevant equations

    [itex]\langle x \rangle = \int _{- \infty}^{\infty} \Psi ^* x \Psi dx[/itex].

    3. The attempt at a solution
    I'm trying to show the first relation. I think I have to do [itex]\frac{d}{dt} \left [ \int _{- \infty}^{\infty} \Psi ^* x \Psi dx \right ][/itex]. But I don't know how to evaluate the integral since Psi is unknown to me. I'm stuck here.
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted