Strong nuclear force Flashcards
The SNF between two nucleons must become repulsive at separations of about _______ otherwise…
0.5fm
otherwise nucleons would pull each other closer and closer together and the nucleus would be much smaller than it is
The SNF has an attractive range between _______ in order to
0.5 and 3-4fm
In order to hold the protons and neutrons together against the electrostatic forces
The effectiveness of the SNF doesn’t depend on _____ and is insignificant at ranges greater than _____ otherwise
charge
a few fm
it would be detected outside the nucleus and neighbouring nucleons shroud the force
Graph of force between nucleons (y axis) against distance from the centre of nucleus / fm (x axis)
Positive y’s = repel
negative y’s = attract
starts from high up and falls below x axis to a minium then curves upwards then 1/x shape along x axis - hits x axis first at around 0.75fm then again at around 3/4fm
Can be the other way around
The strength of the SNF can be estimated by
working out the force of repulsion between two protons at a separation of 1fm, the approximate size of the nucleus. The SNF must be the same magnitude as this force of repulsion - so the SNF > 200N
Increasing separation between nucleons has a greater effect on repulsive electrostatic force than attractive beyond ____
4fm
Effects of the SNF against the electrostatic force depends on
the size of the nucleus
The fact that most nuclei are stable tells us there must be an ______ force, the ______, between any two protons or neutrons in the nucleus.
attractive
SNF
Nucleons are evenly spread at about 1fm in the nucleus and therefore
the SNF acts only between nearest neighbouring nucleons
Shielding =
outer electrons are partially shielded from the attractive force of the protons in the nucleus by inner electrons
Nuclear separation =
1fm
1u =
1.66x10^-27 kg = 931.5MeV = mass of nucleon = 1/12th the mass of C-12 nucleus
1eV =
1.6x10^-19J
1J =
6.25x10^18 eV
Binding energy/mass defect =
931.5MeV/u
