Name the four fundamental forces.

  1. Strong nuclear force
  2. Electrostatic force
  3. Gravity
  4. Weak nuclear force

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Which force is responsible for the repulsion between protons in a nucleus?

The electrostatic force is responsible for the repulsion between protons.

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Which force holds protons and neutrons together in the nucleus?

The strong nuclear force provides an attractive force on protons and neutrons in the nucleus.

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What happens to the strong nuclear force at distances greater than 3 fm?

Above 3 fm the strong nuclear force has a negligible effect.

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What happens to the electrostatic repulsion between protons as their separation decreases?

As the distance between protons decreases, the electrostatic repulsion increases.

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How does the strong nuclear force vary with nucleon separation?

1At distances less than 0.5 fm, the strong nuclear force is repulsive

2Above 0.5 fm the strong nuclear force is attractive

3Above 3 fm the strong nuclear force has negligible effect

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Why do neutrons not feel the electrostatic force?

The electrostatic force only effects particles which are charged. 

The neutron is neutral.

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Which particles in the nucleus feel the strong nuclear force?

Protons and neutrons feel the strong nuclear force.

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What is the exchange particle for the electrostatic force?

The virtual photon (𝛄) is the exchange particle for the electrostatic force.

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What are the exchange particles for the weak nuclear force?

W bosons are the exchange particles for the weak nuclear force.


The W+ boson is positively charged and the W- boson is negatively charged.

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What is meant by the term exchange particle?

An exchange particle is a particle that is emitted or absorbed to 'exchange' a force between two interacting particles. 

Exchange particles are responsible for 'carrying' the four fundamental forces between two interacting particles.

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