Introduction to Physics

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Physics is the branch of science that studies matter, its fundamental constituents, motion and behavior through space and time, and the related entities of energy and force.

The goal of physics is to formulate and test laws that explain all known physical phenomena. These laws govern matter, motion, and energy at both small (microscopic) subatomic distances and at the human scale of everyday life.

Basic Concepts

Physics is a natural science that deals with the interactions between matter and energy. It is one of the fundamental sciences and it covers a huge range of subjects.

The basic concepts in physics include force, motion, energy and light. These are important to understand as they form the foundation of physics and help you answer questions about everyday life.

The scientific approach to physics is to observe phenomena and compare them with the results of theories that explain these phenomena. Theory consists of a set of generalized patterns in nature that are supported by scientific evidence and repeated experiments.


There are many forces that exist in the universe. Forces cause objects to move, change speed or direction, or distort their shape.

There are four fundamental forces in physics: gravity, electromagnetism, the strong interaction and the weak interaction. These all affect everything from the smallest particles to the biggest galaxies.

The strong interaction binds protons and neutrons together in atoms. It is a repulsive force, but it can also be attractive in some circumstances.


One of the key topics in physics is motion. Even though it might seem like nothing is happening, there is always movement happening in the universe.

There are many different types of motion. They include linear, oscillating and rotary motion.


Energy is the capacity for a system to do work. It can be mechanical, chemical, electrical, thermal or any combination of these forms.

It can also be stored in various ways. For example, batteries store chemical energy that is released when they are connected to a circuit and used to power electronics and other devices.

Energy can also be divided into potential energy and kinetic energy. These are determined by how much motion a system can have and how it changes from one form to another.


Light is the electromagnetic radiation that can be detected by our eyes. Its range is extremely broad and varies from low energy radio waves to high energy gamma rays.

Electromagnetic radiation is a form of energy that is created by fluctuations in electric and magnetic fields. This energy transports incredibly fast in a vacuum, at the speed of light.

Although the idea that light is a wave was first proposed by Christiaan Huygens in 1678, modern physics describes it as a stream of massless packets of energy, called photons. It is this description that allows us to understand the interactions of light with matter.


Sound is a vibration that travels through a medium. It is characterized by three properties: speed, frequency and wavelength.

Particles in a medium vibrate back and forth, creating areas of high pressure (compressions) and low pressure (rarefactions). The physical distance between consecutive crests or troughs is called the wavelength.

The expansion of the universe “stretches” the sound waves, lowering their frequencies. But a new computer program is working around that effect by changing the way the components of the sound wave vary in frequency.


Electricity is a fundamental property of matter and a result of the movement of electrons. These particles are small and carry a negative charge.

Electricity is a powerful energy source that we use to operate our cell phones, power trains and ships, run our refrigerators and power motors in machines like food processors. However, it must be transformed to other forms of energy such as heat, light or mechanical energy in order to be useful.

Introduction to Physics

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