What is Nuclear force: Definition and 71 Discussions

The nuclear force (or nucleon–nucleon interaction, residual strong force, or, historically, strong nuclear force) is a force that acts between the protons and neutrons of atoms. Neutrons and protons, both nucleons, are affected by the nuclear force almost identically. Since protons have charge +1 e, they experience an electric force that tends to push them apart, but at short range the attractive nuclear force is strong enough to overcome the electromagnetic force. The nuclear force binds nucleons into atomic nuclei.
The nuclear force is powerfully attractive between nucleons at distances of about 1 femtometre (fm, or 1.0 × 10−15 metres), but it rapidly decreases to insignificance at distances beyond about 2.5 fm. At distances less than 0.7 fm, the nuclear force becomes repulsive. This repulsive component is responsible for the physical size of nuclei, since the nucleons can come no closer than the force allows. By comparison, the size of an atom, measured in angstroms (Å, or 1.0 × 10−10 m), is five orders of magnitude larger. The nuclear force is not simple, however, since it depends on the nucleon spins, has a tensor component, and may depend on the relative momentum of the nucleons.The nuclear force plays an essential role in storing energy that is used in nuclear power and nuclear weapons. Work (energy) is required to bring charged protons together against their electric repulsion. This energy is stored when the protons and neutrons are bound together by the nuclear force to form a nucleus. The mass of a nucleus is less than the sum total of the individual masses of the protons and neutrons. The difference in masses is known as the mass defect, which can be expressed as an energy equivalent. Energy is released when a heavy nucleus breaks apart into two or more lighter nuclei. This energy is the electromagnetic potential energy that is released when the nuclear force no longer holds the charged nuclear fragments together.A quantitative description of the nuclear force relies on equations that are partly empirical. These equations model the internucleon potential energies, or potentials. (Generally, forces within a system of particles can be more simply modeled by describing the system's potential energy; the negative gradient of a potential is equal to the vector force.) The constants for the equations are phenomenological, that is, determined by fitting the equations to experimental data. The internucleon potentials attempt to describe the properties of nucleon–nucleon interaction. Once determined, any given potential can be used in, e.g., the Schrödinger equation to determine the quantum mechanical properties of the nucleon system.
The discovery of the neutron in 1932 revealed that atomic nuclei were made of protons and neutrons, held together by an attractive force. By 1935 the nuclear force was conceived to be transmitted by particles called mesons. This theoretical development included a description of the Yukawa potential, an early example of a nuclear potential. Pions, fulfilling the prediction, were discovered experimentally in 1947. By the 1970s, the quark model had been developed, by which the mesons and nucleons were viewed as composed of quarks and gluons. By this new model, the nuclear force, resulting from the exchange of mesons between neighboring nucleons, is a residual effect of the strong force.

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  1. Aromalsp

    I Decay constant of Different Elements and Isotopes?

    Different elements and isotopes have different rates of beta decay because the half-life of the element or isotope reflects its stability, which is determined by the nuclear force between the protons and neutrons in the nucleus of the atom. The number of protons and neutrons affects the balance...
  2. Cody Livengood

    B Do Alternative Explanations for Gluons Exist and How Can We Test Them?

    I understand how the existence of quarks is inferred from the three particle-emitting cones or jets and by the quarks’ ability to deflect particles passing through the composite particle, but I don’t see how the existence of gluons is conclusively demonstrated by this rather than just being an...
  3. A

    B Is the weak nuclear force attractive or repulsive or both?

    Hi Of the 4 fundamental forces, I did not understand the weak nuclear force. Is the weak nuclear force attractive or repulsive or both? It works between two particles, that is, it is the interaction of two particles?
  4. B

    B Collapse of a neutron star - strong nuclear force vs gravity

    I understand that gravity causes a neutron star larger than about 10 solar masses to collapse into a black hole. I also understand that gravity is the weakest of the four forces. So I find this counterintuitive and I'm puzzled that why is it gravity that causes the collapse and NOT the strong...
  5. K

    I Nuclear Force Behavior: Confusing Isospin Dependence

    Hello! I am confused about when the nuclear force is attractive and when not. Based on deuteron (the book I am following is Wong), we see that we can't have bound state with isospin T=1 (otherwise we would see, for example, a stable double neutron and no proton nucleus). Also, in the book I see...
  6. K

    I What is being plotted in the nuclear potential formula by Samuel Wong?

    Hello! In Nuclear Physics, Second Edition, by Samuel Wong he shows a plot of the nuclear potential (see attached) but he also gives a formula (also attached) for the most general way of writing the nuclear potential. In that formula, we have the coefficients depending on r only, but the overall...
  7. A

    B The Strong Nuclear Force: Is my understanding correct?

    The strong nuclear force is the strongest of the four basic forces in nature (the others are: the electromagnetic force, gravity, and the weak nuclear force). But it also has the shortest range, meaning that nucleons (protons & neutrons) must be extremely close (~1 fm) before its effects are...
  8. F

    Strong Nuclear Force & Particle Accelerators

    I am a teacher and the problem statement is part of our curriculum. I feel like I have a basic understanding of what particle accelerators are, but I only have a vague idea of what the strong nuclear force has to do with this. Here's what I know: In a particle accelerator, you might smash...
  9. Phi6er

    A What is the value of the pion-nucleon coupling constant?

    Links for context: 1. https://en.wikipedia.org/wiki/Yukawa_potential 2. https://en.wikipedia.org/wiki/Yukawa_interaction#Classical_potential I'm working on my BSc right now and I'm solving the energies of 2 nucleon systems (so basically just deuteron) by treating them as non-relativistic two...
  10. Jan Nebec

    B How to calculate the nuclear repulsive force?

    Hello! I'm wondering if there is a simple formula to calculate nuclear repulsive force at given distance between a proton and neutron? For example at 0,5 fm between them... Thank you!
  11. H

    I Is the strong nuclear force stronger than the weak force?

    I've heard that the weak nuclear force is stronger than the electromagnetic force at distances of 10^-18 m. I've also heard that the strong force becomes repulsive at a distance of 0.7 fm. So if two quarks got to a distance of <<10^-18 m which force would win, the strong force or the weak force?
  12. K

    B What causes mass defect in the nucleus?

    Hi. I read that the mass of nucleons in nucleus of Oxygen-16 (or nucleus of another atom) is less than the sum of its nucleons if they were separated (also the mass of 8 protons and 8 neutrons). But why does nucleons have less energy in nucleus of atoms than if they were separated? What causes...
  13. A

    B Weak nuclear force - circumstances in which it is manifested

    I have a glass of water at room temperature. The electromagnetic force is at play between the electrons and nucleus of the atoms, the strong nuclear force is at play holding the nucleus together, the force of gravity weak as it may be is at play between the various particles - electrons, quarks...
  14. G

    I Would Heat Death overcome Strong Nuclear Force?

    Hi, layman here. As I understand, the theoretical Heat Death of the universe would imply that the accelerating space expansion reaches an expansion rate so big that it takes bodies and eventually even fundamental particles apart, leaving them alone up to an ultimate point in which no particle...
  15. hawkeye1029

    Electrostatics and nuclear force problem

    Homework Statement Two protons in an atomic nucleus are typically separated by a distance of 2x10-15 m. The electric repulsion force between the protons is huge, but the attractive nuclear force is even stronger and keeps the nucleus from bursting apart. What is the magnitude of the electric...
  16. Metals

    Questions on the Strong Nuclear Force

    I've been researching and I came across the Strong Nuclear Force. This is apparently the strongest force ever, and only occurs in nuclei at an atomic scale. Now, when a nucleus becomes to big, radiation will occur to decrease its size and return it to a stable state. Does radiation occur...
  17. Sagar Singh

    Strong nuclear force and weak nuclear force

    Hi There! i am little bit confused in between existence of strong and weak nuclear force, can someone please explain about these forces and about their existence
  18. S

    How many times nuclear force is greater than gravitational f

    Homework Statement Homework Equations [/B]The Attempt at a Solution
  19. N

    Can Quarks Break the Strong Nuclear Force?

    Can a black hole at the singularity break the strong nuclear force between two or more quarks creating a free quark? May be a dumb question but I'm no physicist.
  20. X

    Doing a paper on the strong nuclear force --

    I'm doing a paper on the strong nuclear force for a nuclear physics class. I want to give a good quantitative account for it. I'm very familiar with Lagrangian field theory but not so much with QFT or QCD. I don't have time to learn all of the ins and outs of QFT and for this paper and for this...
  21. D

    Binding Energy and Strong Nuclear Force: Exploring a Connection

    Homework Statement I have two questions. 1.The definition of binding energy is the work needed to split the nucleus into its constituent protons and neutrons. The strong nuclear force keeps the nucleus together hence is it right for me to say the binding energy is equal to the energy of the...
  22. D

    Weak Nuclear Force: Electron Ejection Explained

    Is the weak nuclear force really a force? How can an electron be ejected from a nucleus which has many protons; wouldn't positive charges hold it back?
  23. J

    What is the significance of F less than Fmax in the strong nuclear force graph?

    Homework Statement http://www.boredofstudies.org/wiki/images/b/bb/Sci_phys_quanta_strong_force.png I had a question where I was given the strong nuclear force graph and asked to add the electrostatic force to the graph. It was a graph showing the forces between two protons. It was a three mark...
  24. R

    How do the W and Z Gauge Bosons work in the weak nuclear force?

    I've seen explanations that when a neutrino with a W+ Boson comes near a neutron, it affects one of the bottom quarks and changes it to a up quark which effectively turns the neutron into a proton. The neutrino then turns into an electron. Source: (2:20 onwards) I've seen other explanations...
  25. avito009

    Why is the strong nuclear force the strongest of the four fundamental forces?

    Is more force required at smaller distances like the nucleous of an atom? Since strong force applies itself at the level of the atom does that prove that more force is required at smaller distances to attract according to the inverse square law? Does strong nuclear force obey the inverse square...
  26. A

    Nuclear force tensor operator expectation value.

    Homework Statement I have a question asking me to find the expectation value of S_{12} for a system of two nucleons in a state with total spin S = 1 and M_s = +1 , where S_{12} is the tensor operator inside the one-pion exchange nuclear potential operator, equal to S_{12} =...
  27. M

    What's the relation between Mass Defect and the Strong Nuclear Force?

    Hello. Sorry for being annoying, I've posted like three questions today. But I'm studying nuclear chemistry and still somewhat confused regarding the binding energy and mass defect and their relation with the strong nuclear force.. 1) in this Hank Green video... He says that the mass defect...
  28. T

    Why is the strength of weak nuclear force important ?

    I am just a student. I read that if the strength of weak nuclear force were stronger than current value, this would cause the rarity of neutrons. And, if the strength of weak nuclear force were weaker than current value, this would cause most of hydrogen to convert to helium. I can't understand...
  29. I

    Inflationary Cosmologys effects on the strong nuclear force

    Not sure if this is a cosmology or standard model question , but here it goes. If the repelling force caused by inflationary cosmology were strong enough (perhaps down the line a few hundred quadrillion years from now or so) to begin to create space in between quarks, will the strong nuclear...
  30. M

    Why is the strong Nuclear force the strongest?

    And the electromagnetic force stronger than gravity? That is what is written everywhere about the fundamental forces. It is simply because we don't generally see or observe matter (if at all such matter exists) having a mass to charge ratio high enough to make the magnitude of...
  31. H

    Mass-Energy Equivalence and Storng Nuclear Force

    This really isn't a homework question per se, but I really don't want to post in the big boys' fora. I am learning about basic modern physics at school, as the title suggests, but I am very confused on one matter. Take the tritium nucleus as an example. If tritium nucleons are separate...
  32. C

    Comparison of strong nuclear force and electromagnetic force

    How much stronger is the strong nuclear force compared it to the electromagnetic force beyond what could be accounted for by the inverse of the distance squared?
  33. A

    How to calculate the nuclear size from the strong nuclear force?

    I suppose that the evaluation of the size of a proton and of nucleons calculating the equilibrium between the repulsive electric force and the attracting strong nuclear force is a standard nuclear physics topic, but I couldn't find it. Can anyone help?
  34. G

    Strong Nuclear Force: Exploring the Relationship Between Distance and Force

    Hi all, I read a while ago that there was a force that increased as distance increased. So I went to look around, and I read that it is supposedly the "strong nuclear force". However, reading up on the details, it didn't really seem to be the case at all. I found this image for the...
  35. A

    Notation for Weak Nuclear Force Particles

    The notations are: W^+, W^-, and Z^0. I'm assuming the W stands for Weak. But, why Z for the neutral one? Is there even a reason?
  36. S

    What is the relationship between the weak nuclear force and charge?

    Hi PF I was wondering today about the origin of the fundamental forces. Now gravity comes from mass (lets call this massive charge), electromagnetism comes from electrical charge and the strong force comes from color charge. These are all kinds of "charges", but what kind of "charge" gives...
  37. E

    Time Irreversibility and the Weak Nuclear Force

    I've been writing a lot recently about whether the reason for the increase of entropy over time (i.e. the second law of thermodynamics) is the time irreversibility of the weak nuclear force. I would like to get some people's thoughts on this topic (perhaps links to important papers on this...
  38. W

    Nuclear Force Problem: Showing Unbound Neutron-Proton State & Energy

    How to show that neurton-proton state is unboud, and what is its energy ?
  39. A

    2 strong nuclear force questions

    How is it possible that the strong nuclear force is directly proportional to distance? How could all the atoms in the universe be so far apart if this were the case? The fact that I can't find an equation for the strong nuclear force makes me think it's just not that simple. Could someone tell...
  40. P

    Gravity as a Residual Effect of the Strong Nuclear Force?

    Couldn't gravity just be a residual effect of the strong nuclear force? We know that the manner in which a proton's quarks share a gluon is imperfect on a quantum level - i.e., the gluon exhibits its effect beyond just a single proton - and this is why nuclear fusion can occur. Isn't it...
  41. S

    Purpose of the weak nuclear force?

    Can someone explain in layman terms the purpose/function of the weak nuclear force?
  42. F

    A massive force carrying particle? The weak nuclear force, the W boson has mass?

    I was looking at the list of the force carrying particles and all of their masses read zero other than the W boson of the weak nuclear force. Q: Does the W boson travel at the speed of light even if it is massive? (I am guessing not) Q: If the W boson is massive then it emits other gauge...
  43. D

    Nuclear force between neutrons

    Why is it that neutrons don't stick together? As far as I know the nuclear force is also acting between 2 neutrons and not just between neutrons and protons. So why are there no ultra dense neutron objects consisting of a large number of neutrons, except of course for neutron stars where...
  44. C

    What is the weak nuclear force

    is the weak nuclear force what binds atoms together to make molecules?
  45. FeDeX_LaTeX

    Clarification on Weak Nuclear Force

    Hello; I don't know a lot about the weak nuclear force, so I wanted to ask if some of these statements are correct; -The weak nuclear force is what is responsible for radioactive decay -When alpha and beta radiation occurs, the W+, W- and Z0 bosons are what carry the radiation force -The...
  46. F

    Do Neutrons Feel Strong Nuclear Force?

    do neutrons also feel strong nuclear force and if they do how is that possible because they are uncharched and no force is required to keep them together ?
  47. W

    Nuclear force as residual color force

    Hi all, I'm can't wrap my head around this. I get how the strong interaction bonds quarks into baryons and I get the pion exchange model for the attraction between nucleons (well sort of, I still don't understand how exchanging massive particles can result in an attractive force, but OK)...
  48. D

    Limit at which Strong Nuclear force = Electromagnetism

    Is there a defined distance at which Electromagnetism starts exerting more force than the strong nuclear force? So far I have Gluons have <20MeV (32.04×10-13J) of energy. Using the uncertainty principle: t=h/(4×pi×E) and distance = t×c Therefore t = (6.6×10^-34)/(4×pi×<32.04×10^-13)...