1800-1023-196

+91-120-4616500

# Nature of Physical Laws

## Introduction of Physical Laws Fig 1: The role of physicist is to analyze and simplify natural phenomena

The role of physicists is to explore the universe and unlock its secrets. The investigations and research of physics are determined from microscopic to the macroscopic world. Physical laws simplify complex understanding of natural phenomena in form of mathematical equations and concepts.

When we try to observe and designate a natural phenomenon we need to be aware of many measures and details about the objects involved in a physical process. There are two types of quantities involved in a physical process. They are:

• Constant Quantities
• Variable Quantities

### Constant Quantities

The quantities which remain constant during a natural process are called constant quantities. These quantities are also known as conserved quantities as they are conserved in nature. Understanding conserved quantities help in studying physical phenomena and summarizing them quantitatively. How conservation principles help in studying physics are as follows:

• Whenever a body free fall under gravity, its mechanical energy ( sum of kinetic energy and potential energy) is conserved
• Although kinetic energy ( energy due to motion of an object) and potential energy ( energy due to relative position of an object) change at every second during free-fall of an object but the sum ( mechanical energy is constant)

### Variable Quantities

The quantities which change during a natural process are called variable quantities. These quantities make physics more interesting and flabbergasting. You must have observed the sudden change in climate and direction of the wind at the time of raining. This is how physics affect daily life and procedures. Variable quantities complex natural phenomena, so scientists prefer to perform experiments in constant conditions to get desired results.

Example: When a stone and feather are dropped from a height, the variable quantity involved is acceleration. Both stone and feather are meant to be dropped in an environment where air resistance is not involved.

Ask: How conservation laws help us in real life?

## Conservation Laws in Physics Fig 2: Example of Law of Conservation of Mass

Concepts of energy play a central role in physics. Every physical phenomenon involves the transfer of energy to execute itself. Energy can be seen or felt in many forms, for example, heat energy used in engines, Electrical Energy which is responsible for providing electricity to the country etc. Every energy transfer works on energy conservation laws. The Law of Conservation of Energy states that total energy of a closed system is conserved, adding further energy can neither be created or destroyed but can transfer from one form to another.

Examples

• When a moving car hits a parked car, the parked car moves, that is the energy from moving car is transferred to the parked car
• When we kick a football on the ground, our muscular energy is converted to kinetic energy of the ball

Just like other laws, conservation laws hold good only in certain experimental conditions. If you analyze the mechanical energy of a freely falling body under gravity in open environment you’ll get to know that law isn’t working. This is because of air resistance which hinders some flow of energy of a falling body. But if the same experiment is performed in a closed environment, you’ll find the law of conservation of energy holds good.

The law of conservation of energy is valid on both microscopic and macroscopic world of physics. This helps in understanding microscopic and macroscopic phenomena.

## Applications of conservation of Laws

• Used in the analysis of nuclear, atomic and elementary processes in particles.
• The total energy of the universe is constant and works on this law
• In analyzing a chemical reaction quantitatively i.e. amount of reactants and products involved

## Chemical Reaction and Conservation of Laws

Fig 3: Rearrangement of Atoms in formation of Water

A Chemical Reaction is simply a rearrangement of atoms among other molecules. In a chemical reaction, the conservation law holds for mass. It means mass can neither be created nor be destroyed but it conserved in a chemical reaction. If the energy is released in a chemical reaction, then the chemical reaction is called exothermic reaction. If the energy is involved or given in a chemical reaction, then the chemical reaction is called endothermic reaction.

## Physics and Energy

Fig 4: Energy equation proposed by Albert Einstein

Energy forms the basic existence of physics and its utilization. Scientists always thought that there must be a relationship between energy and mass. Later on, Albert Einstein proved this relation with his famous energy equation.

E = mc2

Where E denotes Energy, m denotes mass of particle and c is the speed of light (3×108 m/s)

Einstein energy equation proved that mass and energy are interconvertible. This equation framed the basics of nuclear physics and helps in releasing energy in nuclear power generation and nuclear explosions by fission and fusion of radioactive elements.

## Conclusion

Fig 5: Physicists use conservation laws to understand natural phenomena

Apart from being simple and general, conservation laws are very useful in real life application of physics. Some applications of conservation laws are as follows:

• When we solve a complex dynamics problem involving lot of particles and forces, we use conservation laws to get desired results
• Analyzing velocity in a collision between two automobiles can be complicated when we consider internal contact forces during a collision. But with the help of law of momentum we can obtain the velocities of the automobiles easily
• Neutrino was discovered in 1931 by Wolfgang Pauli with the help of conservation laws and momentum principle

The laws of nature don’t change with time. If you perform any experiment today and repeat the same experiment after 10 years (under same experimental conditions) you will get the same result. Adding further laws of nature are same at every location, it doesn’t matter if you perform the experiment in India or France, and the results are likely to be same. However some conditions do change by differing location, for example, the acceleration due to gravity on earth is six times that of the moon, but the law of gravitation is same on both celestial bodies. It concludes that physical laws of nature are Symmetrical and Conservative in nature.

Watch this Video for more reference