Strong Force: Definition, Equation & Examples

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  • 0:00 Chemistry 101
  • 0:36 What is the Strong Force?
  • 1:16 How the Strong Force Works
  • 2:38 Lesson Summary
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Lesson Transcript
Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

In this lesson, you'll learn what strong force is, how it holds an atom together, and how it is balanced by electromagnetic repulsion. A short quiz will follow.

Chemistry 101

Have you ever wondered how the atom is held together? When people sit in chemistry class, a lot of the time they don't notice an inherent issue in the structure of the atom. The nucleus of the atom contains neutrally charged neutrons and positively charged protons. Opposite charges attract and like charges repel, just like with the north and south poles of a magnet. So how is it that the positive protons stick together? Shouldn't they be running away from each other as fast as they can?

Well, they actually should. And the reason they don't is because of the strong nuclear force.

What Is the Strong Force?

In physics, there are four fundamental forces: gravity, the electromagnetic force, the weak force, and the strong force.

The strong force is, unsurprisingly, strong. The strong force is the force that holds the nucleus of the atom together, even though other forces want to pull it apart. The electrostatic repulsion, part of the electromagnetic force, between the positive protons in the nucleus is very powerful. So the strong force has to be strong to overcome this. The strong force only works in the nucleus of the atom. This is because it has a very short range. Even the electrons are too far away to be affected by the strong nuclear force.

How Strong Force Works

There's another thing you might not have noticed in chemistry class. As you go down the periodic table into larger and larger atoms, the number of neutrons starts to balloon rapidly. From atoms like Helium, which has two protons and two neutrons, the same number of each, you quickly get to the point where there are far more neutrons than protons, an effect that only gets more crazy the further down you go. There is a reason for this, and again, it's because of the strong force.

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