There are four universal or fundamental forces in nature. Without these forces, all matter in the world will fall apart. Force as such is any pull or push that causes an object to alter its physical state (in terms of motion or deformity). Newton defined a force as anything that causes an object of mass ‘m’ to move with an acceleration ‘a’.

1. Gravitational Force

Why is the universe not filled with floating human beings and cows and cars and other such things? Obviously because the gravitational force of the earth holds us to the planet. Gravitational force is the force responsible for holding planets in their orbits and this is possible only because of their infinitely long range.

Gravitational force can be represented as follows:

where,

\(F_g\) is the gravitational force
\(G\) is the universal gravitational constant
\(m_1\) and \(m_2\) are the masses of the objects in consideration
\(r\) is the distance between the centres of the two objects in consideration

When considered for massive objects, like the sun, or giant planets, gravitational force is considered to be strong as the masses of these objects are also large. On an atomic level, this force is considered weak.

2. Electromagnetic Force

Did you know that you have never truly ever touched anything in the world? You are matter and we know that all matter is made up of atoms. Atom in turn has a dense nucleus, protons, neutron and electrons. And where are these electron? They occupy the outermost layer of an atom. Now what is the charge on electrons? They have negative charges.

By their nature, all particles are only attracted to particles that have an opposite charge and repel those with like charges.

Say you feel like holding a pen. The pen is matter made of atoms filled with nuclei, neutrons, protons and electrons spinning around the nucleus as well. By nature, the electrons that you are made of and the electrons that make up your pen will repel each other. So technically, you never truly touch anything!

These are electromagnetic forces. Why does a comb get charged when you continuously brush your hair? Why are the subatomic particles held together? Because of electromagnetic forces!

These have a long range and the effect of their forces diminishes over distance due to shielding effect. However, sub-atomically, they have short range and are considered strong forces but still weaker than strong nuclear forces.

3. Strong Nuclear Forces

Out of the four fundamental forces, nuclear forces are the strongest attractive forces. Electromagnetism holds matter together, but there was no explanation on how the nucleus is held together in the atom. If we consider only electromagnetism and gravity, then the nucleus should actually fly off in different directions. But it doesn’t, implying that there exists another force within the nucleus which is stronger than the gravitational force and electromagnetic force. This is where nuclear forces come into play. Strong nuclear forces are responsible for holding the nuclei of atoms together.

Same charged protons attract each other due to Nuclear force.

This is the most dominant force in reactions and is so strong that it binds protons with similar charges with the nucleus. It is mostly attractive in nature but can be repulsive sometimes. It has a very short range of just 1 fm.

4. Weak Nuclear Forces

Weak nuclear forces are responsible for the radioactive decay, specifically the beta decay neutrino interactions. It has a very short range (less than 1 fm) and this force is weak in nature.