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Homework Help: Momentum in Quantum Mechanics

  1. May 2, 2006 #1
    Problem 1.17 in griffiths gives, at time t = 0, the state psi =A(a^2-x^2) for -a to a, and 0 otherwise. It asks then to find the expected value of momentum p at 0 and also the uncertainty in p. How do I do this? The only way momentum is defined is md<x>/dt, and since the state is only for time t, there seems to be no way to do this.

    I know that if i take fourier transform the wave function i'll get the expected momentum, but I don't think that's what the problem wants me to do. Is there a simpler way?
     
  2. jcsd
  3. May 2, 2006 #2
    never mind, i'm an idiot.
     
  4. May 2, 2006 #3

    Tom Mattson

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    Glad we could help. :biggrin:
     
  5. May 3, 2006 #4
    :rofl: :rofl: :rofl:
     
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