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: Force between particles in nucleus

  1. Jan 12, 2010 #1
    1. The problem statement, all variables and given/known data

    The nucleus of a zinc atom has 30 protons and 35 neutrons, and a diameter of 4.00 x 10^-13 m.
    What is the minimum repulsive electrostatic force between two protons in the nucleus.

    2. Relevant equations

    3. The attempt at a solution
    Not sure how to approach this. I understand that the minimum force will be when these protons are furthest apart. How do I calculate the maximum distance between the protons in the nucleus?
    Using Electrostatic Force = -DeltaPotentialEnergy/distance?

    I can calculate the spherical area of the nucleus, and calculate the number density of the protons, but I don't see how this helps. I could use ElectricalPotentialEnegy = q1q2/(4pi perm0 r) and use the known charge of a proton, but I still have two unknowns (r and Potential Energy).
    Any ideas?
  2. jcsd
  3. Jan 12, 2010 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    You seem to be overthinking this problem.

    Imagine two particles are confined to be within a sphere of diameter D. How far apart can the two particles get?
  4. Jan 12, 2010 #3
    Well, I see what you're saying for two particles. But if two protons in the zinc nucleus experience a repulsive force as a result of being at either end (maximum distance apart), then what about the repulsive force as a result of all of the other protons? How can I just ignore that?
  5. Jan 12, 2010 #4
    Forget it - I've just realised that the question is only asking for the force between the two protons in question...
    Thanks for your help.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook