1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: Minimum kinetic energy

  1. Apr 13, 2010 #1
    36. A proton is confined in a uranium nucleus of radius 8 x 10^-15 m. Determine the proton's minimum kinetic energy according to the uncertainty principle if the proton is confined to a one-dimensional box that has length equal to the nuclear diameter.

    What's wrong with my equation and value I used for L^2?

    362.jpg
     
  2. jcsd
  3. Apr 13, 2010 #2
    You defined [tex]L = 2\Delta x[/tex] so that means L should be the diameter and not the radius of the nucleus.
     
  4. Apr 13, 2010 #3
    Son of a... It does say diameter. :rolleyes: And so delta-x is the radius.

    Where did the 8 come from?
     
    Last edited: Apr 13, 2010
  5. Apr 13, 2010 #4
    I think the 8 came from if you pulled the 2 from 2*r out of the square it would be 4. And then you would have 2*4 = 8.
     
  6. Apr 13, 2010 #5
    But the 1.6 x 10^-5 nm = 2r, so that term is already squared. She has 8*m*d^2, not 2*m*(2r)^2 which would be 8*m*r^2.

    The definition of delta-x is arbitrary, right? But it has to make sense in the context of the wave function. It seems that delta-x = L/2 is a common definition.
     
    Last edited: Apr 13, 2010
  7. Apr 13, 2010 #6
    I think your grader just corrected it twice. Not thinking that you would interpret at as a single correction.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook