Sir Isaac Newton was an English physicist who gave the three laws of motion stated in his book entitled Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy). The force and laws of motion form the basis of modern physics. Newton’s three laws of motion revolve around the aspects of inertia, force and action-reaction. Experiments and observation were done for over 200 years, to verify the enunciated laws of motion by Newton. These laws were further used to study and explain the motion of numerous physical bodies and systems that gave rise to the foundation of Newtonian mechanics.

What is a Force?

The word force is often used to indicate an action when we try to pull or push any object. By applying a push force, we tend to keep it away from us whereas when applying a pulling force, we tend to bring the object close to us. Simply we can absorb that force is a medium of interaction between the two objects. The SI unit for the quantity force is Newton (symbol ‘N’).

Force can be classified into two large categories namely,

  1. Contact forces: examples such as friction, the tension in a spring, spring force etc.
  2. Non-contact forces: examples such as gravitational force, magnetic forces etc.

The four major types of forces that prevail in nature are as follows:

  • GRAVITATIONAL FORCE

There is a presence of attraction between the two objects by the virtue of their masses.

 

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  • ELECTROMAGNETIC (EM) FORCE

Besides gravitational force, the two bodies might exert electromagnetic (EM) forces of some magnitude on one another because the bodies possess charge.

  • NUCLEAR FORCE

 In this case, When the interacting particles are protons or neutrons or both of them, and in other cases as well, nuclear forces come into action. Anything that involves changes within the nucleus, there is a presence of nuclear forces.

The phenomena of radioactivity, nuclear fission, nuclear fusion etc. result from nuclear forces.

  • WEAK FORCES

The reactions that involve particles such as protons, electrons and neutrons usually involve weak forces.

For example, changes like beta plus (β+) decay and beta minus (β-) decay, occur due to the presence of weak forces. As the name suggests, the magnitude of such force is very less.

Define Newton’s Law

Newton’s law gives a relationship of the forces acting on an object and the motion exhibited by that object with each other. We can derive various principles and concepts from Newton’s proposed laws. 

The first two laws given by Newton demonstrate the type of motion exhibited by the object when various forces act on it whereas the third law tells about the action-reaction concept between the two objects in nature. The following terms are pre-requisites to understanding the fundamental Newton’s laws-

  • Force: It is a vector quantity that shows the interaction between two objects.
  • Mass: It is the amount of matter present in a body.
  • Acceleration: It refers to the rate at which the velocity of an object/body changes with respect to time.

Force and Laws of Motion

Sir Isaac Newton enunciated the three laws of motion. The fundamental essence of Classical physics is the concept of Newton’s laws of motion. The interrelationship between force and laws of motion is crucial. 

Newton’s First Law of Motion

  • Also called the ‘Law of Inertia’.
  • According to the first law of motion, the particle remains to be unaccelerated only when the sum of all the forces acting on that object is zero.
  • Fnet  = 0
  • Application: The motion of a kite when there is a change in direction of the wind, the motion of any object falling through the atmosphere etc.

Newton’s Second Law of Motion

  • The acceleration shown by a particle, when observed through an inertial frame is dependent on the sum of all the forces acting on that particle and the mass of the particle.
  •  Fnet  = m * a

where Fnet  is the total (net) of all the forces exerting on the particle

 m is the mass of the particle

 a is the acceleration of the object

  • Application: the motion of a spaceship or aircraft as a result of weight of the aircraft, thrust applied and aerodynamic forces.

Newton’s Third Law of Motion

  • Colloquially known as ‘action and reaction law’.
  • It states that if an object P exerts a force on the other object Q, the object Q will exert a force of equal magnitude and in the opposite direction on the object P. Hence, it is called an action and reaction pair. 
  • Application: when firing a bullet, the bullet undergoes an accelerating force in a forward direction whereas the gun recoils in an opposite direction. 

Conclusion

Force and laws of motion are intertwined and are revolutionary in the field of science having their everyday applications in life. Force is a vector quantity that tells about the interaction between the two particles. The concept of laws of motion given by Sir Isaac Newton in 1687 from classical mechanics gave birth to the basis on which modern physics is founded.