Finding Momentum and Uncertainty in Quantum Mechanics Problem 1.17

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Homework Help Overview

The discussion revolves around a quantum mechanics problem from Griffiths concerning the expected value and uncertainty of momentum for a given wave function defined in a specific range. The original poster expresses confusion about how to approach the problem, particularly regarding the definition of momentum in relation to the time-dependent state.

Discussion Character

  • Exploratory, Conceptual clarification

Approaches and Questions Raised

  • The original poster considers using the Fourier transform of the wave function to find the expected momentum but questions whether this aligns with the problem's intent. They express uncertainty about the appropriate method to apply given the time constraints of the state.

Discussion Status

The discussion appears to be in an early stage, with the original poster seeking clarification on the problem's requirements. There is no consensus reached, and some participants have made light-hearted comments without contributing to the problem-solving process.

Contextual Notes

The problem is constrained by the specific form of the wave function and the requirement to find expected values and uncertainties in momentum, which may not be straightforward given the initial conditions provided.

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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?
 
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never mind, I'm an idiot.
 
Glad we could help. :biggrin:
 
Tom Mattson said:
Glad we could help. :biggrin:
:smile: :smile: :smile:
 

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