What is an example of the strong nuclear force?

Question:

What is an example of the strong nuclear force?

Fundamental Forces:

A force can be thought of as something that pushes or pulls on matter. According to the Standard Model of particle physics, there are four fundamental forces that govern the pushes/pulls (or we can say interactions) between particles that have mass. They are the strong force, weak force, electromagnetism and gravity. The strong force is an attractive force. It pulls together neutrons and protons within the nucleus of an atom.

Answer and Explanation: 1

When someone asks about the strong nuclear force they are usually asking how it is that protons can stay together in the nucleus of an atom given that they have a positive charge. A property of electromagnetism is that opposite charges attract and like charges repel. All atoms, except hydrogen, have more than one proton, as well as neutrons, making up the nucleus. Neutrons have no charge, but because protons have positive charges, they should repel each other. The reality is that they do. But the multi-proton nucleus is also real. This contradiction led to the hypothesis that there must be a force stronger than electromagnetism that can create a stable nucleus.

The strong interaction is divided into two parts - the true strong force and the nuclear force. The true strong force is what is happening inside protons and neutrons, rather than between them. Protons and neutrons are also referred to as nucleons. Nucleons are not fundamental particles; rather, they are made of truly indivisible particles called quarks. Each nucleon is made of three quarks. Protons are made of two up quarks and one down quark (referred to as uud), and neutrons are made of two down quarks and one up quark (referred to as udd).

The strong interaction keeps the three quarks in very close proximity to each other which is necessary to maintain the structure of the nucleon. Physicists discovered that the three quarks continuously emit and reabsorb a massless particle called a gluon. Gluons are the force-carrying particles of the strong force. As quickly as a quark emits a gluon it is reabsorbed by one of the other quarks. This constant exchange of gluons keeps the quarks from flying apart.

The nuclear force is an indirect result of this exchange of gluons by quarks. The nuclear force binds nucleons together allowing the atomic nucleus to exist. Remember that protons naturally repel and so the EM force must be overpowered by a stronger force. However, nucleons do not directly exchange gluons. Rather, they exchange particles called pions. Pions are made up of a quark and antiquark as well as the gluons they are exchanging just like happens within a nucleon. This is why we can say that the strong interaction indirectly creates the nuclear force.

While the strong force and nuclear force are stronger than the EM force, their effect is only over a very short distance - no more than the diameter of the nucleus. When the nucleus of an atom becomes very heavy the EM force overtakes the strong force and the nucleus becomes unstable. This seems to happen in atoms above the atomic mass of lead. These heavier atoms are radioactive and naturally go through nuclear decay - a process mediated by another fundamental force, the weak force.


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Strong Force: Definition, Equation & Examples

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Chapter 7 / Lesson 16
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Explore the fundamentals of the strong nuclear force. See the strong nuclear force definition and understand how it works. Discover various strong force examples.


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