What are Different Types of Forces

At a fundamental level, there are only four different types of forces in physics. These are strong nuclear forces, electromagnetic forces, weak nuclear forces, and Gravitational forces. Below is the description of each force.

Strong Nuclear Forces

Comparatively, this is the strongest type of force. According to the Standard model, gluons are the exchange particles for this force. Strong nuclear force holds quarks inside hadrons, and it is also responsible for holding protons together inside the nucleus, without them flying apart due to electrostatic repulsion.

Electromagnetic Forces

Electromagnetic forces act on electric charges. It is responsible for keeping protons and electrons together in atoms. Most everyday phenomena observed in electricity and magnetism are governed by this force. The exchange particle for electromagnetic force is the photon.

Weak Nuclear Forces

Weak nuclear forces are responsible for beta decay. The exchange particles are the W and Z bosons.

Gravitational Forces

Gravity is responsible for the attraction between masses (and consequently, gravity is responsible for planetary orbits). Comparatively, gravity is much weaker compared to the other three types of forces, and why this is so remains one of the greatest unsolved mysteries in physics. Gravity does not fit well within the standard model, which does a good job at explaining the other three types of forces. Gravitons are often used in some theories to describe a fundamental particle that would mediate gravitational forces, however such a particle has never been discovered.

When we deal with classical physics problems, it is often helpful to imagine other additional kinds of forces. For example, normal contact force or reaction force, tension, friction, electrostatic force, magnetic force, weight, etc.

Normal Contact Force (Reaction Force)

When a body pushes against a surface, the surface exerts a force on the body that is perpendicular to the surface. This force is called the normal force or the reaction force.

Tension

When a cord is attached to a body and is pulled taught, tension is the force that acts along the cord, in a direction pointing away from the body.

Friction

When two surfaces move against each other, there is a force that opposes the motion, which acts on a surface against its direction of motion. This force comes about because, on a microscopic scale, the surfaces are rough, and they consist of protrusions. When the objects move against each other, these protrusions can interlock and delay the objects’ motion.

Electrostatic Force

The force of attraction or repulsion between two charged objects.

Magnetic Force

The force of attraction or repulsion between two magnetic materials.

Weight

The force of gravity is acting on a body.  If the acceleration due to gravity is given by $g$, then, the weight $W$ acting on an object with mass $m$ is given using Newton’s second law as:

$W=mg$

Near the Earth’s surface, $g=9.81$ m s-2.

To reiterate, at a fundamental level, most of the forces we encounter in our daily lives (with the exception of gravity) are various forms of electromagnetic forces. For instance, normal contact force comes about from the repulsion of electrons making up the two bodies that are in contact.