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Heisenberg's uncertainty principle

  1. Jun 1, 2015 #1
    1. The problem statement, all variables and given/known data
    Find the minimum uncertainty of the momentum of a small particle with mass m=1g, which is confined within a region of width a=1cm.

    2. Relevant equations
    Delta(p)*Delta(x)>=hbar/2

    3. The attempt at a solution

    Delta(p)*Delta(x)=hbar/2
    Delta(p)*10^(-2)=hbar/2
    Delta(p)=10^2*hbar/2

    This looks pretty straightforward to me, but the given mass in this problem is what confuses me.
     
  2. jcsd
  3. Jun 2, 2015 #2

    rude man

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    I think you have it right & putting in the mass is a red herring. Maybe they meant to ask for the minimum uncertainty in the velocity.
     
  4. Jun 2, 2015 #3
    You might want to scan this:

    http://en.wikipedia.org/wiki/Particle_in_a_box

    Pull quote:

    "The uncertainties in position and momentum ( b56546a86ab832a9b2a5b15f96519319.png and 7aa41487a1a40b0077afa0c3331ba111.png ) are defined as being equal to the square root of their respective variances, so that:

    a83e98aee94cda7f0410e16698b54ebf.png
    This product increases with increasing n, having a minimum value for n=1. The value of this product for n=1 is about equal to 0.568 9dfd055ef1683b053f1b5bf9ed6dbbb4.png ..."
     
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