Science Articles

Laws of Motion – Sir Isaac Newton

Born on 4th January 1643 into a Puritan family in Woolsthorpe, England; he was one of the greatest Mathematicians of his generation and a well-known physicist. He invented the calculus in the mid to late 1660s and is well known for the formulation of the theory of universal gravity. If you haven’t guessed the name yet, he is none other than Sir Isaac Newton.

Newton lost his father before he came into this world. After his mother remarried, he was brought up by his grandmother. Though he wasn’t a bright student during his schooling years, he took up Law at the Trinity College Cambridge. He learnt maths, physics, astronomy and optics by himself. After completing his famous work on the three laws of motion, Newton got his master’s degree. Besides this, his work on gravity has also been his best work.

“To myself I am only a child playing on the beach, while vast oceans of truth lie undiscovered before me.”

– Sir Isaac Newton

What Are Newton’s Three Laws Of Motion?

Isaac Newton’s three laws of motions describe the motion of massive bodies and their interaction with each other. Isaac’s work became the foundation for modern physics. After 18 months of intense work, he published his laws in 1687 ‘Philosophiae Naturalis Principia Mathematica’ which explains how massive bodies move under the influence of external bodies. They are sometimes called a Newtonian reference frame.

Newton’s First Law Of Motion:

‘A body at rest will remain at rest, and a body in motion will remain in motion unless it is acted upon by an external force.’

This first law is also known as the law of inertia. This conceptual jump was just the beginning.

For example, a train is moving at high speed as is everything inside of it. Ahead the signal turns red, and the train driver stops the train abruptly. While the train has stopped moving, the passengers are still in the momentum, and in the state of inertia, they get a jerk and move forward and back until they sit still.

Newton’s Second Law Of Motion:

‘The force acting on an object is equal to the mass of that object times its acceleration.’

F = ma (where F is the force, m is mass and a is acceleration)

Let’s say you are riding your bicycle. When you pedal, you can control the speed of the bicycle as soon as you push on the pedals of the bicycle the speed of the bicycle increases. This demonstrates Newton’s second law of motion.

Newton’s Third Law Of Motion:

‘For every action, there is an equal and opposite reaction.’

When one body exerts a force on the other, the second body also exerts an equal force on the first body as force occurs in pairs. This interaction between two bodies is seen in everyday life.

For instance, when you are skipping with a rope, your legs apply force to the ground, and the ground applies an equal and opposite force that thrusts you to jump.


The three laws of motion helped explain Isaac Newton arrive at the theory of gravity. In Newton’s theory of gravitation, when two objects attract each other, the forces of the gravitational attraction is directly proportional to their masses and inversely proportional to the square of the distance between their centres.

These laws have been instrumental in understanding every other motion in the universe, such as the reason why the moon revolves around the Earth and the planets revolve around the sun. This helped Newton to understand the flattening of the Earth at the poles, and the gravitational force of the sun and moon create the tides.