# Laws Of Conservation

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In any physical process involving the different forces, some physical quantities remain changed with time. Such quantities are called conserved quantities. The law which govern the conservation of these quantities are called conservation laws.

A conservation law is a hypothesis, based on observations and experiments. It cannot be proved, it can be verified or disproved by experiments.

There are four laws of conservation in classical physics. These are as follows.

## 1. Law Of Conservation Of Energy

Law of conservation of energy states that energy can neither be created nor destroyed but it can be changed from one form to another. The total energy sum of all kinds of energy in this universe remains same.

## 2. Law Of Conservation Of Mass

It was assumed that mass is indestructible and law of conservation of mass states that matter can neither be created nor destroyed.

But Einstein’s theory of relativity (E= mc²) modified it and we still use it as a very important principle, except in nuclear reactions. The conservation of rest mass into other forms of energy is so small that to a high degree of precision, rest mass may be thought of as conserved.

## 3. Law Of Conservation Of Momentum

Momentum is the quantised effect of motion of a moving body. It is measured as the product of mass and velocity of the body. It is a vector quantity. Momentum of an isolated system is also conserved.

Momentum can be classified into two types and law of conservation is valid for both of them.

(a) Law of conservation of linear momentum.

(b) Law of conservation of angular momentum.

## 4. Law Of Conservation Of Charge

This law states that the total charge of an isolated system remains constant. This implies that the electric charge can neither be created nor destroyed, only they can be transferred from one body to another.