**Physical World **

Gravitational force and electromagnetic force are experienced in the physical world.

Because the range of both of them is infinite.

Whereas in the microscopic world, nuclear forces, electric and magnetic forces and weak nuclear force are experienced in radioactive shadows.

The fundamental forces in nature are :

**1.Gravitational force**

**2.Electromagnetic force**

**3.Strong nuclear force**

**4.weak nuclear force**

**Gravitational Force**

It always arises in nature between two bodies due to their masses.

It is always the force of attraction.

According to this force,

**The gravitational force between any two objects is proportional to the product of the masses of the two objects and inversely proportional to the square of the distance between them.**

Suppose two objects whose masses are m1 and m2 respectively and the distance between them is r.

Hence the gravitational force between them,

F∝1/r²______(2)

From equation (1) and (2)

F∝m₁.m₂/r²

**F=G.m₁m₂/r²**

Where G is a constant. Which is called universal gravitational constant.

and its value,

It is 6.67×10⁻¹¹ N.M²/Kg².

Therefore, gravitational force is also called universal force.

**Electro Magnetic Force**

It is a force acting between charged particles. If the charges are at rest at a certain distance, the force acting between them is called electrostatic force. Which was studied by Coulomb.

Hence it is also called Coulomb force.

According to this force,

**The Coulomb force between any two stationary charges is proportional to the product of the two charges and inversely proportional to the square of the distance between them.**

By combining equations (1) and (2)

F∝q₁.q₂/r²

F=K.q₁.q₂/r²

Where K is a constant.

Its value,

1/4Ï€€o=9×10⁹ N.M²/C²

Where €o is dielectric constant of vacuum.

Its value,

8.86×10⁻¹² Kg²/NM²

The value of K depends on the permittivity of the medium.

When a charge is moving, a magnetic force also acts on it. Generally electric and magnetic fields cannot be separated. Because a changing magnetic field generates the electric field.

Therefore, the electric and magnetic fields which cannot be separated are jointly called electromagnetic fields and the forces arising from these fields are called electromagnetic forces.

**Strong Nuclear Force**

This force arises between neutron-neutron, proton-proton, proton-neutron.

In modern discoveries, strong nuclear force also arises between quart-quart because protons and neutrons are made up of microscopic particles like quart.

### Properties of strong nuclear force

It is the strongest force in nature. The strong nuclear force is 100 times stronger than the electromagnetic forces.

This force does not depend on charge.

This force is a force with short range (10⁻¹⁵m). It is affected only within the nucleus.

In some nuclear events like Î²_decay of radioactive nucleus, the force acting between the elementary particles is called weak nuclear force.

**Weak Nuclear Force**In some nuclear events like Î²_decay of radioactive nucleus, the force acting between the elementary particles is called weak nuclear force.

**Note**- Î² is a radioactive nucleus, emitting one electron and one antineutron.

The weak nuclear force is also a force with a weak range (10⁻¹⁶m) and it is stronger than the force of gravity.

All fundamental forces are derived from the exchange of a particular characteristic particle.

**Gravitational force – arises from the exchange of gravitons.**

**Electromagnetic force – obtained from exchange of photons.**

**Strong nuclear force – obtained from the exchange of mesons between nucleons.**

**Weak nuclear force – obtained from Bosan exchange**.

**Nature of physical laws**

Some conservation rules are as follows:

**Conservation of energy**

**Conservation of linear momentum**

**Conservation of angular momentum**

**Mass energy conservation**

**Conservation of charge**

**Conservation of energy**

**Conservation of linear momentum**

**m₁v₁+m₂v₂+m₃v₃________+mâ‚™vâ‚™= constant**

**Conservation of Angular momentum**

torque Ï„=0

J₁+J₂+J₃_____+Jnâ‚™=fixed

m₁v₁r₁+m₂v₂r₂+______+mâ‚™vâ‚™râ‚™=constant

**Angular momentum- The moment of linear momentum is know as angular momentum.**

**Mass-Energy conservation**

Mass and energy are not separate physical quantities but are two forms of the same quantity.

The Mass can be converted into energy and energy can be converted into the mass.

Equivalent relation between mass and energy

**E=mc²**

where c is the speed of light

**c=3×10⁸ m/sec**

**Example---**

In a nuclear reaction, the total number of nuclei remains constant, whereas the total mass of the nuclei reacting in the process does not remain constant before and after the reaction but varies. This difference is called mass loss. And this mass loss appears as energy.

**Conservation of charge**

**Example---**

Pair production

Pair destruction

## Purpose and stimulation of physical

Physics is basically divided into two parts

- Gross
- Micro

### Under the micro and macro influence of physical

Events related to atoms and nuclei are explained. Modern quantum mechanics is used to study it. Along with this, the composition and structure of matter and the interactions between particles etc. are studied.

Thus, physics is a macro and micro science and is the basis of all branches of science, that is, in physics, the phenomena of the non-living world are studied, which are beneficial for living beings.

In this, the laws of solid, liquid and gas are studied. It is based on Newton's laws of motion and the law of gravity. In this branch, physical quantities like mass, inertia, force, energy, power etc. are explained.

**Branches of Classical Mechanics**

**1. Mechanical**

**2. Thermodynamics **

**3. Optics**

**4. Oscillations and waves**

- Free
- Damped
- Forced

**5. Electrodynamics**

## 0 Comments

## Post a Comment