## Basic Forces in Nature

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Table Of Content

## Definition

Basic forces in nature are the forces governing macroscopic as well as microscopic world. These are gravitation forces, weak forces, electromagnetic forces and nuclear forces.

## Introduction

In daily life, we come across many kinds of forces like friction forces, electrostatic forces, magnetic forces, viscous forces etc. These forces are observed to be acting between macroscopic objects. For instance, while walking on rough horizontal surface, the frictional forces are acting between our feet and rough surface. All the forces that we feel in macroscopic world are categorized basically into two groups

• Gravitational forces
• Electromagnetic forces

Besides these, there are two more forces acting in microscopic world and those forces are

• The weak (nuclear) forces
• The (strong) nuclear forces

Hence, four types of basic forces are actually governing macroscopic as well as microscopic world.

These are:-

1. Gravitational Forces
2. Electromagnetic forces
3. Weak forces
4. Nuclear forces

### Gravitational Forces

Issac Newton discovered that every particle in the universe attracts another particle with some force. That force of attraction is called gravitational force.

In the figure, two particles of masses m1 & m2 are separated by a distance ‘r’, the force of attraction is given by

Where, G is universal gravitational constant and its value is

The gravitational force are appreciable only if atleast one of two bodies has a very large mass.

#### Salient Feature

(i) Gravitational force is conservation forces.
(ii) There are the weakest forces in nature

### Electromagnetic Force

Forces executed by one particle on another because of the electric charges on the particles are called electromagnetic forces. If charges are alike forces are repulsive otherwise forces are attracting in nature.
According to coulomb’s law, if two charges q1 & q2 are separated by distance r1 ,the electromagnetic force between them is given by

is a constant and

is absolute electrical permittivity of free space.

#### Salient Features

1. These forces may be attractive or repulsive
2. They obey inverse square law
3. They operate over distances which are not very large
4. They are central forces
5. They are also conservative forces

### Weak Forces

The weak force is the force of interaction between elementary particles of short lifetimes. The leptons are class of elementary particles and include electrons, neutrons, muons & their anti-particles. The weak forces come into action for interaction between two leptons or between lepton & meson and between lepton & baryon. Ex., the process of β-decay is due to weak interaction. The β-decay is represented by

In the process of β-decay, a neutron inside the nucleus changes into a proton by emitting an electron and an unchanged particle called anti-neutrino.

During weak interaction, the two particles are in contact or exactly overlap each other.

### Nuclear forces

The force that binds neutrons & protons together in a nucleus is called the strong nuclear force. It acts between two protons or two neutrons or a proton & neutron. Nuclear force is attractive in nature and it is 10 times stronger than repulsive electric force between two protons. It is due to strong nuclear force that nucleus is a stable structure.

#### Salient features

• These are the strongest force in nature
• Nuclear forces have the shortest range
• They do not obey inverse square law
• These are charge independent
• These are non-central forces
• They are also non-conservative forces