Fundamentals of Physics

Fundamental Forces in Physics

These four forces are separated due to their differences in force strength, what can interact with them, and how far of a range they can affect.

Gravitational Force

The first of these forces is the gravitational force. It is a force that only affects bodies that possess mass, causing them to exert a force on any other bodies that possess mass as well. The gravitational force is always attractive, that is, all objects with mass will tend to move toward each other. For example, the Earth’s mass affects the Moon, causing it to orbit around us, but the Moon’s mass also affects the Earth, changing the tides and causing waves. The Earth is affecting the Moon a lot more due to the massive difference in mass.

An image of Earth, showing the direction in which gravitational forces act upon it. Wikimedia Commons

Electromagnetic Force

The electromagnetic force is what affects all electric charges, the nature of their attraction and repulsion to one another, and why an electric charge is capable of forming a magnetic field in the right conditions. The electromagnetic force is far stronger than the gravitational force but acts on a much smaller scale.

Strong Force

The strong force is more complicated, in the fact that it exclusively acts between particles on the atomic level. Even smaller than atoms, the building blocks that make them up are known as subatomic particles such as protons and neutrons, and even smaller still are quarks, the base building blocks that make up everything. These quarks are held together by the strong force, which in turn has their forces that aid in holding together the protons and neutrons that make up atoms as well.

An example of a nucleus with arrows showing the direction the strong force acts in to bind protons and neutrons together. Wikimedia Commons

Weak Force

The weak force is even more complicated still, being present in radioactivity, particularly as it decays but also in these radioactive processes present in the sun.

Fundamental Laws of Physics

In the universe, there are rules that all objects have to obey, no matter what, they are the rules of reality. These concepts are some of the most vital laws that affect us every day.

The Laws of Motion

The three laws of motion explain how bodies can move within this universe, as well as how their movement is governed by external forces, and how a body will move in reaction to these forces. These laws are attributed to Isaac Newton and are also known as Newton's laws of motion.

1. The first law of motion is the law of inertia, which states that if a body or object has no forces acting on it at a given time, it will stay in motion if it is in motion, or it will stay at rest if it is at rest.

2. The second law of motion states that if a resultant force is acting on an object, it is a product of both mass and acceleration, expressed as \(F=ma\).

3. The third and final law of motion states that if body A is exerting a force onto body B, then body B will in turn produce a force equal in magnitude but opposite in direction upon body A.

The Law of Electromagnetism

Electromagnetism affects our lives in many different ways, but at a base level, it describes how electric currents and magnetic fields are related. When an electric current flows, it will in turn produce a magnetic field. This magnetic field’s strength depends on the strength of the current and the number of loops in the coil of the wire that the electric current is flowing through.

Electromagnetism’s most important feature in our lives is its help in creating the Earth’s magnetic field or magnetosphere. Through the electric current passing through molten iron in the Earth’s core, a massive magnetic field is generated around the entire planet, extending far into the atmosphere. This magnetic field protects us from many harmful things that occur in space, most commonly radiation emitted from our own Sun. Without this protection, the heat we would experience from this radiation would make the planet impossible to live on.

The Laws of Thermodynamics

The entire field of thermodynamics revolves around four laws, all of which describe in some way how energy and temperature behave and interact with one another.

1. The first law of thermodynamics is simple, it states that energy can never be created or destroyed. It is only possible for energy to be converted into another form of energy.

2. The second law states that if an energy conversion occurs involving heat energy, this conversion will be irreversible, and always tend towards a more disorganized form. This is also known as entropy.

3. The third law states that this previously mentioned entropy within a system that involves the conversion of heat energy will reach an eventual constant value as the temperature in this system reaches absolute 0, also known as -459.67 degrees Fahrenheit.

There is another law known as the zeroth law of thermodynamics. This law shows us that a system will always aim to achieve thermal equilibrium, which is the state of everything in the system being at an equal temperature.

The Law of Relativity

General Relativity is a very complicated topic that we could go into in great detail, but here we will describe it in a basic way, covering only the fundamental aspects of the concept.

General Relativity describes how matter and energy give rise to gravity. It is, in essence, the study of space and time on a massive scale. It explores the concept of a so-called space-time that can be bent and curved by matter and forms the basis for modern-day cosmology.

The theory of General Relativity was built upon the theory of Special Relativity which describes how physical quantities can be measured differently by observers in relative motion.

Fundamental Physics Equations

If you know anything about physics, then you know there are usually equations involved in any topic. Thousands upon thousands of equations, but a lot less than that could be considered fundamental. Here are a few examples of fundamental equations:

Speed

Speed is how long it takes something to travel a specific distance. Speed is calculated by:

\(v=\frac{d}{t}\),

where \(v\) is speed, \(d\) is distance, and \(t\) represents time.

Acceleration

Acceleration is the rate of change of speed, meaning how quickly something increases or decreases in speed. Acceleration is calculated by:

\(a=\frac{v-u}{t}\),

where \(a\) is acceleration, \(v\) is the final velocity, \(u\) is the initial velocity, and \(t\) is the time.

Weight

Weight is the force applied to bodies of mass by gravity. It is calculated by:

\(W=mg\),

where \(W\) is weight, \(m\) is mass, and \(g\) is the acceleration due to gravity.

Ohms Law

Ohms Law describes the relationship between voltage (potential difference), current, and resistance. The equation is:

\(V=IR\),

Where \(V\) is voltage, \(I\) is current, and \(R\) is resistance.

Frequency

Frequency is the number of complete wave cycles that can occur over a second. Frequency is calculated by:

\(f=\frac{v}{\lambda}\)

Where \(f\) is frequency, \(v\) is the speed of the wave, and \(\lambda\) is the wavelength of the wave.

Fundamental Units in Physics

When we think about the most important units in the field of physics, the first thing that comes to mind is the International System of Units, or SI units for short. These seven units are the main units used for their respective measurements, and all other units can be written as a combination of these units. The units are:

• The \(\mathrm{meter}\) is the SI unit of \(\mathrm{length}\), with the symbol \(\mathrm{m}\).
• The \(\mathrm{kilogram}\) is the SI unit of \(\mathrm{mass}\), with the symbol \(\mathrm{kg}\).
• The \(\mathrm{second}\) is the SI unit of \(\mathrm{time}\), with the symbol \(\mathrm{s}\).
• The \(\mathrm{ampere}\) is the SI unit of \(\mathrm{electric\:current}\), with the symbol \(\mathrm{A}\).
• The \(\mathrm{kelvin}\) is the SI unit of \(\mathrm{temperature}\), with the symbol \(\mathrm{K}\).
• The \(\mathrm{mole}\) is the SI unit for the \(\mathrm{amount\:of\:substance}\), with the symbol \(\mathrm{mol}\).
• The \(\mathrm{candela}\) is the SI symbol of \(\mathrm{light\:intensity}\), with the symbol \(\mathrm{cd}\).