A force is an influence exerted that can alter the motion of any object. It can cause a body to accelerate from a state of rest. A force carries weight and has direction, making it a vector quantity. It’s important to understand the basic concepts regarding force to better our understanding of important topics in physics. Force is essentially the push or pull of an object. This push or pull can result from phenomena such as gravity, magnetism etc. It is usually denoted in equations as the letter F, and the SI Unit of Force is Newton (N). 

Historical Development of the Concept

Since ancient times, thinkers have pondered how to describe the concept of force aptly. They used this concept to study the movement of objects, stationary objects and simple machines. 

Thinkers such as Aristotle and Archimedes made errors in understanding force, owing to the antiquity of their times and their inability to understand frictional force. Subsequently, these errors were corrected by Sir Isaac Newton and Galileo Galilei. This gave the world an accurate idea about the concepts of forces.

Sir Newton proposed three laws of motion, which were developed and used to introduce forces. Albert Einstein provided further research on the topic through his theory of relativity, which developed new information about the forces of gravitation and inertia. 

Formulas for Force 

The formula derived through Newton’s Second Law of Motion states that Force(F) = mass(m) x acceleration (a). The formula is used in mathematical equations involving the calculation of force applied. 

The SI unit of force is Newton. Sometimes, Dyne is also used as a unit of force. Force is expressed in kgm/s². One Newton is equal to 105 Dyne. 1 Newton is the amount of force required to accelerate 1 kilogram of mass at one metre per second squared. 

Initial Classification of Forces

There are a number of examples of different types of forces around us. Forces can initially be classified into balanced or unbalanced forces. 

1. Balanced Forces: Two forces that act on an object in opposite directions and are the same size are balanced forces. A balanced force results in the object remaining stationary. We see balanced forces in action in hanging things, floating or static objects. 
2. Unbalanced Forces: When two forces acting on an object are not the same in size, we refer to it as an unbalanced force. An unbalanced force causes stationary objects to start moving, change direction, change speed, or compel a moving object to stop. We see many examples of unbalanced forces around us every day. 

The balanced and unbalanced forces are not the only ones to be studied under the introduction to forces. The classification of forces can also take place into fundamental and non-fundamental forces. 

Fundamental Forces

Major Forces on the planet can be classified into four types. These are gravitational forces, electromagnetic forces, strong and weak nuclear forces. These are known as fundamental forces, as the rest of the forces derive themselves from these. 

1. Gravitational Force: Gravitational Forces were discovered and researched by Sir Isaac Newton when he connected objects falling to the surface of the earth to the motions of planets around the sun. Gravitation force, briefly, is the force that attracts objects towards each other. Gravitational force grows as the mass of the object increases. It is responsible for attracting all objects on the earth’s surface towards the centre of the earth. 
2. Electromagnetic Forces: Michael Faraday and James Clark Maxwell demonstrated the theory of electromagnetism, uniting the electric and magnetic forces. It was initially described by Coulomb as a force existing between two charges. By understanding electromagnetic forces, we know that a magnetic field is developed when current is introduced in a conductor. 
3. Strong Nuclear and Weak Nuclear: These forces exist within atoms and are crucial for the functioning of the universe. A strong nuclear force counters the repulsion between similarly charged particles in the nucleus of the atom. A weak nuclear force is central to nuclear decay, converting a neutron into a proton. The strong and weak nuclear forces helped form stars, galaxies, and planets.

Non-Fundamental Forces

These forces exist as a result of the fundamental forces. Some of the non-fundamental forces are:

Frictional Forces: It refers to the force generated by two objects sliding against each other. Friction is the force that resists motion during the contact of two surfaces. The frictional force depends on the type of surface, the angle, and the object’s position.  

1. Tension: Tension refers to the force exerted on a pulley or a rope when it is pulled through opposite ends. It acts on the entire cable/rope and is exerted through opposite sides. Tension is the action-reaction pair of forces that takes place on the same object.
2. Elastic: It is the force that allows objects to return to their original size after expanding or stretching. Like a bungee cord or a rubber band, some cables exert a counterforce known as an elastic force in the opposite direction of expansion. It initially stops the expansion and brings back the object to its original shape.

Conclusion

In simple words, a force can be described as a pull or push that an object faces when it interacts with another object. The forces can be divided on the basis of their strength and direction – balanced or unbalanced forces. They can also be divided based on their characteristics, such as frictional, tensional, and elastic forces.