# Physics Overview

by Ron Kurtus

Physics is the study of the properties of matter and their relationship with energy and forces. It is a branch of Physical Science.

Objects are made of matter and vary in size from extremely large to extremely small. Energy concerns the velocities of objects. Applying a force to an object can result in its motion.

The study of physics can be divided into classical physics, relativity, and quantum mechanics. Classical physics concerns everyday sizes and velocities. Relativity concerns large objects and high velocities, while quantum mechanics concerns extremely small sizes and distances. Both areas use complex and high-level mathematics.

Most of our studies will be on classical or everyday physics.

Questions you may have include:

• What is classical physics?
• How is relativistic different?
• What is quantum mechanics?

This lesson will answer those questions. Useful tool: Units Conversion

## Classical physics

Classical physics is also called traditional physics, because it concerns everyday phenomena, sizes, and velocities. Isaac Newton is credited with many classical physics theories.

The subject is divided into several branches of study:

• Matter
• Mechanics
• Wave motion
• Heat energy
• Electricity and magnetism
• Gravity and gravitation

### Matter

The study of matter includes the various states of matter and their properties.

### Mechanics

Mechanics—or classical mechanics—concerns forces and the motion of objects. This includes the different forms of energy: kinetic, potential, as well as radiation.

### Wave motion

Wave motion is a special application of mechanics. It mainly concerns sound waves and electromagnetic waves. There are general wave characteristics that apply to all waveforms.

#### Sound waves

Acoustics—or the study of sound—concerns the motions of the particles of air or other medium through which sound waves can travel.

#### Electromagnetic waves

The study of electromagnetic waves—or optics—is the study of visible light, infrared radiation, radio waves, microwaves, ultraviolet radiation, and x-rays. All these waveforms affect matter differently, but have the properties of reflection, refraction, interference, diffraction, dispersion, and polarization in common.

### Heat energy

Heat is the internal energy of a material. Thermodynamics concerns the relationships between heat and other forms of energy.

### Electricity and magnetism

Electricity and magnetism covers:

• General electricity
• Static electricity
• Direct current (DC) electricity
• Alternating current (AC) electricity
• Magnetism
• Electromagnetism

### Gravity and gravitation

Gravity and gravitation concerns the force of gravity near the Earth and the forces of gravitation in space.

## Relativistic mechanics

Relativistic mechanics or relativity concerns what happens to matter, space, and time at extremely high speeds or velocities. Relativity uses high level mathematics to make its predictions. Albert Einstein is usually associated with the study of relativity.

There are two main areas of relativity:

• Special Theory of Relativity
• General Theory of Relativity

### Special Theory of Relativity

The Special Theory of Relativity concerns the relative uniform motion of objects in a straight line, especially as they approach the speed of light, causing changes in size and time.

### General Theory of Relativity

The General Theory of Relativity concerns accelerated motion that explains gravitation, where matter curves space.

## Quantum Mechanics

When distances and objects become extremely small, motion is no longer continuous. Instead, discrete—or quantum—motion is seen. This happens at the atomic and subatomic level.

Many classical laws of physics no longer apply, including the fact that particles also exists as waves. The mathematics to study quantum mechanics is highly complex.

### Quantum Field Theory

While Special Relativity concerns large velocities and Quantum Mechanics concerns small distances, there is a disconnect between the two theories. Quantum field theory concerns both small sizers and large velocities as an effort to unify quantum mechanics and special relativity.

There are a number of theories that try to unify quantum mechanics and relativity.

## Summary

The study of physics can be divided into classical physics, relativity, and quantum mechanics. Classical or everyday physics concerns normal speeds, distances, and sizes. Relativity concerns large objects and high velocities, while quantum mechanics concerns extremely small sizes and distances.

Try to understand the world around you

## Resources and references

Ron Kurtus' Credentials

### Websites

Physics - Wikipedia

Outline of Physics - Listing of subjects - Wikipedia

The Physics Classroom - Physics lessons

Physics.org - Physics lessons and science news

Physics Resources

### Books

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## Students and researchers

www.school-for-champions.com/science/
physics_overview.htm

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