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: Uncertainties in the momentum and kinetic energy of the proton?

  1. Apr 7, 2010 #1
    1. The problem statement, all variables and given/known data
    A proton in a tin nucleus is known to lie within a sphere whose diameter is about 2.2 multiplied by 10E-14 m. What are the uncertainties in the momentum and kinetic energy of the proton?

    2. Relevant equations
    delta(x)*delta(p) >= hbar
    delta(E)*delta(t) >= hbar

    3. The attempt at a solution

    I understand the first part finding the uncertainty of the momentum, which is simply. . .

    1.05E-34 J(s) / (2.2E-14 m) = 4.77E-21 kg(m/s)

    I don't however, in any way understand finding the uncertainty in the kinetic energy. . . Howe are we suppose to know this if we aren't told the time (or does that matter). I know the answer should be something times E-14, but I would like to know how to modify and manipulate this equation (delta(E)*delta(t) >= hbar.

    Any help would be appreciated.
  2. jcsd
  3. Apr 8, 2010 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    I think you just need to find the kinetic energy corresponding to the momentum you have calculated.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook