May 18, 2020
Matter is composed of molecules that are in turn composed of atoms -- electrons gravitating around a small dense nucleus of protons and neutrons. These tiny particles have different intrinsic physical properties, such as a mass, an electric charge and a spin.
Elements composing matter are interacting with each other mainly through the concept of forces.
A force is a representation of the physical interaction between two bodies (particles, molecules, objects); where one body is capable of giving an acceleration to the other (that is, to change its speed).
In nature, there are only 4 fundamental forces that can explain all the interactions in our world:
The mass is one of the few intrinsic characteristics of matter. This property defines the quantity of inertia a body has. It plays a role in the relationship between a force and the resulting acceleration of a body, through Newton's second law of mechanics (stating that the force equals the mass of a body multiplied by its acceleration). This property also rules the gravitational interaction between two bodies. Indeed, Newton's also discovered that two bodies with given masses are interacting together by attracting each other with a force that depends on both masses.
IF you hold an apple with your hand and suddenly drop it, it will fall down on the floor. This is due to what we call its "weight", which is a force applied by the Earth onto the apple. Two masses attract each other with a force that is proportional to their distance and to their masses:
W = G. (m1m2)/r^2
The strong and weak nuclear forces are forces that rule the sub-atomic world. The distance on which these forces can act are very small, on the order of the size of the atom itself and they do not play a role in computers; but are indispensable to maintain the atoms and their composing particles together.
The electromagnetic force regroups the electric force that relates to the electric charge of electrons and the magnetic force that relates to the spin of electrons.
The force applied on a moving particle q of velocity v inside an environment where an electric field E and a magnetic field B is present is equal to:
F = qE + qv x B