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Homework Help: Velocity neutron in vacuum

  1. Dec 8, 2012 #1
    1. The problem statement, all variables and given/known data
    What is the de Broglie wavelength of a neutron that has fallen 0.60 in a vacuum chamber, starting from rest?

    2. Relevant equations
    Not entirely sure

    3. The attempt at a solution
    I can't figure out what the velocity is, I think it would have to do with the change in kinetic energy but I can't figure out what that would be
  2. jcsd
  3. Dec 8, 2012 #2


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    Staff Emeritus
    Science Advisor

    Is the distance 0.6 m, cm, mm? Units, as well as magnitude, are rather important to a physics or engineering, or other quantitative problem.

    If the neutron is in freefall - what is the acceleration? Knowing the acceleration and distance, one can determine the velocity at that distance.
  4. Dec 8, 2012 #3
    The other way to look at it, instead of calculating accelerations and integrating back to get velocity, is to look at the Energy. The change in energy is just mg*(change in height) and this goes into the kinetic energy i.e. 1/2 mv^2.
  5. Dec 8, 2012 #4

    I tried finding the velocity using v2=2ax
    and found v to be 3.43m/s
    then I plugged that into λ=h/mv
    where m=1.67*10-27kg and h=6.67*10-34
    and found λ=5.87*10-8
  6. Dec 8, 2012 #5
    wait for some reason I was using h=3.36E-34 instead of 6.67E-34 I don't even know where that number came from
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