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!

B What causes mass defect in the nucleus?

  1. Sep 15, 2017 #26
    Isn't this some kind of random? depending on the nucleon and it is position? You may average the energy loss across them and calculate the mass but that isnt accurate.

    You could do it though for simple atoms right?
  2. Sep 15, 2017 #27


    User Avatar
    Science Advisor

    Does a nucleon actually have a position in a nucleus?
  3. Sep 15, 2017 #28
    Uhh probably something with quantum mechanics..

    All the animations shows them vibrating around which doesn't give a definite position and most likely that they are wrong on some level(Yes, I know it is wrong to think of them as little balls). My question should be doesn't each nucleon contribute differently than others? and does it even make sense to talk about mass loss of a single nucleon?
  4. Sep 15, 2017 #29

    Well, if a nucleon does any work, then its energy and its mass decrease. Conversely, if nucleon's mass never changes, then we can guess that the nucleon never does any work.

    Now let us consider macroscopic objects: Two metal spheres, one is positively charged, other one is negatively charged.

    The spheres are floating in viscous oil and are being pulled towards each other by the coulomb force. The energy and the mass of the sphere-pair is decreasing, so the sphere-pair is doing work.

    But the sphere on the right is not losing mass, so it is not doing any work, and same is true for the sphere on the left.

    The sphere-pair is doing work - to be more specific the electric field of the sphere-pair is doing work, but not the electric field of the sphere on the left or the electric field of the sphere on the right.

    As the sphere-pair loses mass, it floats a little bit higher in the oil. The sphere on the right has not lost any mass, but it floats higher.

    That last sentence seems problematic to me. Did I make some error??
  5. Sep 17, 2017 #30

    Well I have thought about it, and the solution to the problem seems to be this: We do not say that the metal sphere on the left has a reduced mass, instead we say the left side of the system has a reduced mass. Somehow that seems to make the problem disappear. :smile:

    We have the word nucleon, so how about if we do not call a free proton or neutron a nucleon, but instead we call them a proton and a neutron?

    And those nucleon particles that can be thought to exist inside nuclei, how about if we do not say that they are protons and neutrons and have the same masses as protons and neutrons? Is it not a naive idea that nucleons would have the same masses as protons and neutrons?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted