Classification paragraph

Force is an influence that affects objects, changing for example its structure, speed and  direction. In the SI system force is measured in Newtons and it is usually described by the formula F = ma, Force equals mass times acceleration. Forces split into two categories, fundamental and non-fundamental forces. Fundamental forces are the ones that are responsible for the atomic and subatomic interactions. Such force is electro-magnetism which occurs because of the different electric charges between protons and electrons, it is responsible for the shape of atomic matter but it also occurs out of the microscale. Another fundamental force is gravity, which is the force between any objects anywhere in the universe, it is relative to the mass and the distance between the objects. Non-fundamental forces are the forces that exist only on the macroscale and are caused by the fundamental forces that were mentioned earlier. An example of a non fundamental forces is friction which is caused when two surfaces meet, it is always opposed to the direction of the velocity and its potency depends on the roughness of the surface. These forces can all be calculated with modern day physics and it is used to help us understand how the universe works.