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Minimum energy of electron bound in nucleus

  1. Nov 11, 2012 #1

    An electron is confined to a nucleus of radius 4 femtometres. Estimate its minimum energy.

    2. Relevant equations


    As the electron's rest energy will be much less than it's kinetic energy,


    3. The attempt at a solution

    So I understand that I'm supposed to use the uncertainty principle to find the average momentum, and then plug it into the energy equation. What I don't understand is that the solutions use Δpx/2 instead of just Δpx. Why is this?
  2. jcsd
  3. Nov 11, 2012 #2


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    I think that Δpx/2 in both directions gives a difference of Δpx, which is "somehow" equivalent to a momentum uncertainty.
    Using Δpx is probably fine, too.

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