Isaac Newton's Law of Gravity

Gravity is a mysterious force. This force pulls all things towards earth. Every object in the universe has gravity, but not all amounts are the same. For example; items like the earth have a higher amount of gravity than others. The mass of the object is what determines the amount of gravity, this is why the earth and the sun have more gravity than say an apple. Another factor determining the amount of gravity is the distance between the object and you, if there is a shorter distance between two objects, the gravity will be stronger.

Without gravity we could not survive. Gravity is the force keeping us centered on the earth, therefore if there was no gravity we would just float off into the atmosphere. The importance of gravity also relates to the sun - the gravity of the sun keeps earth in the same orbit of the sun. Without this gravity, the earth would drift off, losing the sun’s light and warmth which is needed for earth to survive or it would drift to close causing earth to heat up rapidly ending all living species.








Johannes Kepler, a German mathematician and astronomer, established three laws in the early 1600’s that would define the movement and motion of the planets about the sun. Although these three laws of planetary motion set the basis for defining paths and motion of planets about the sun, they didn’t explain why these paths and motions occur. Johannes just recommended that some sort of interaction between the sun and the planets existed, and that this interaction between the planets and sun caused a driving force for the planets motion. Isaac Newton was bothered by this description. He thought that there must be some cause for this force causing the planets to stay in the suns orbit.



(Johannes Kepler)

With Kepler setting the basics for gravitational forces, Isaac Newton later was able to describe his astronomical observations with the idea of a force (known as gravity). This also led him to discover that the earth was not the center of the solar system; all other planets and the sun orbit instead the sun was the center and the other planets orbited the sun. Isaac newton also later found out that the moon is kept in the earth's orbit due to gravity. He found out that without gravity the moon would drift off in a straight line rather than circling the earth.

Gravity is everywhere as stated in Newton’s universal Law of Gravity, "every object in the universe that has a mass exerts gravitational pull, or force on every other object with a mass." The strength of the gravitational pull an object gives off depends on the mass of the object. For example; us - humans give off a gravitational pull but as we are not very big the gravitational pull is not very strong. Therefore the environment around us isn’t centered around us, although our gravitational pull isn’t very strong it would be stronger than the gravitational pull of a dog. An example of strong a gravitational pull is the earth. It has a strong enough pull which keeps the moon in the same orbit while also keeping the things that live on its surface grounded. Without this gravitational pull the moon would drift away messing with the tides and we would float into space. This shows how important gravity is, as without we would not be able to carry out our daily routines.




The moon doesn’t crash into the earth as it is exerting its own gravitational force but the earth is bigger and exerts a stronger gravitational pull, therefore the moon orbits the earth instead of the other way around.

The earth’s gravitational pull moves all objects with a smaller gravitational pull towards its center, therefore if you were to drop a ball from the top of a tree it would fall in the direction of the earths center but would stop when the ball it the ground as it cannot push through the earth’s crust. The earth exerts the same gravitational pull on every object although some think it doesn’t. An example of this is when you drop a feather, the feather falls to the ground but it falls every slowly. This is not because there is not a strong enough pull it is because of air resistance. As air is all around us it can slow down the falling time of a light object as it cannot push through the air, it doesn’t mean than the earth is exerting a weaker gravitational pull.




Isaac Newton’s universal law of gravitational force was formed after he observed an apple fall from a tree, the story goes that he asked the question why? Why did the apple fall? Using his mathematical background and Kepler’s framework he came to the conclusion that the force between two objects is equal to universal gravitational consent known as gravity times the mass of the first object, times the mass of the second object and then divided by the distance squared. The equation looks like this below:

F= force of gravity between two objects
G=the universal gravitational consent (6.67×10-11)
M1=the mass of object one
M2= the mass of object two
R2= the distance between the two objects (squared)


For example:
I am standing five meters away from a dog (from core to core), my weight is 63kg and the dog’s weight is 34kg. The force between us is


F= 6.67×10-11) x (63) x (34)
                                   (5)2


F= 0.00000000571 Newtons

Below is a brief video explaining the Law of Gravity:

Revolution of Calculus

Sir Isaac Newton (a British Scientist) was the first person to fully develop calculus which caused a revolution of mathematics. Modern physics and physical chemistry would be impossible without it. Other academic disciplines such as biology and economics also rely heavily on calculus for analysis.

His theory of calculus built on earlier work by his fellow Englishmen John Wallis and Isaac barrow, as well as on work of such continental mathematicians as Rene Descartes, Pierre de Fermat, Bonaventura Cavalieri, Johann van Waveren Hudde and Gillies Personne de Robserval. Unlike the static geometry of the Greeks, calculus allowed mathematicians and engineers to make sense of the motion and dynamic change in the changing world around us, for example the orbits of the planets and the motion of fluids.

The initial problem Newton was confronting was that, although it was easy enough to represent and calculate the average slope of a curve because the slope of a curve was constantly varying, and there was no method to give the exact slope at any one individual point on the curve i.e. effectively the slope of a tangent line to the curve at that point.

Newton had a huge impact on society. His studies in mathematics led to the formation of modern calculus. Through his formulas, ways were found to solve areas space occupied by anything placed along a curved surface. That was by far his greatest accomplish in the field of maths. In the modern day Isaac’s ideas are now called differential calculus, integral calculus and differential equation.

Newton choose not to publish his revolutionary mathematics straight away, worried about being ridiculed for his unconventional ideas, and contented himself with circulating his thoughts among his friends. leibniz published in 1684, newton published in 1693. Today, people give equal credit to Newton and Leibniz for calculus’s discovery.

The Laws of Motion

Isaac Newton’s Laws of Motion are made up of three essential laws in classical physics. His discovery of the laws of motion came upon after watching an apple fall when studying the effects of gravity. It is assumed that this incident and his curiosity as to why the planets above us do not fall to the ground, led him to establish the laws of motion. In 1686 he published his three laws of motion.

Isaac Newton’s first Law of Motion is also referred to as the ‘Law of Inertia.’ This law is usually stated as, “an object at rest stays at rest, while an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.” There are two sections to this statement. The first being the one that predicts the behaviour of moving objects and the other is the prediction of the behaviour of stationery objects.

The behaviour of all objects can be explained by stating that objects tend to “keep on doing what they’re doing,” unless they are acted upon by an unbalanced force. Isaac Newton discovered this first law of motion by realising that a mysterious force made an object in motion stop. He identified that the mysterious force was friction. Friction makes moving things slow down and stop, without friction moving objects would keep going forever.

For example; a person playing golf.

A golf ball is on the ground. It cannot miraculously move into the hole unless some kind of force will act on it. The person using the golf club and hitting the ball is the force. The balls will now move, proving the first part of Isaac Newton’s first law of motion. The law also states that the ball will stay in a state of constant velocity in the absence of an unbalanced force. This means that there is no frictional or any other force and the ball will never stop. Although, when we throw a ball we always see it stop…there is a reason behind this. If the ball is hit into the air and then drops to the ground, the ground is the force of friction making the ball slow down and eventually stop moving. This is the unbalanced force.

Isaac Newton’s second law of motion:

Isaac Newton’s second law of motion states that “acceleration is produced when a force acts on a mass. The greater the mass of the object being accelerated the greater the amount of force needed to accelerate the object.”

Everybody unintentionally knows Newton’s second law of motion. If you want to move something heavier the same distance as a lighter object…the heavier object is going to require more force.

For example; a heavy rock needs to be moved.

A young child wants to move a rock by pushing it. The rock moves slightly. If an adults pushes the rock, the rock will move a greater distance. This proves Newton’s second law of motion. The child applies less force so less acceleration is produced. The adult applies more force and more acceleration is produced. Therefore, force is equivalent to acceleration.

An object with a smaller mass means that the amount of applied force needed to move it is less, whereas something with a greater mass requires more force to move it. This force is called a Net Force which is the overall force acting on an object.

The amount of force needed to push an object is equal to the mass of an object and the force is also equal to the acceleration needed to push an object. This means that force equals the product of mass and acceleration.

Force = Mass                                                             Force = Acceleration

This law can be expressed in a mathematical equation:

F = M A

FORCE = MASS times ACCELERATION

The standard metric unit of force is given in Newtons, (N).

Quick examples:

Net Force (N)	Mass (kg)	Acceleration (m/s/s)
10	2	5
20	2	10
20	4	5

Newton’s third law of motion:

Newton’s third and final law of motion states that “for every action there is an equal and opposite reaction.” This law relates to the ability of force. A force is a push or a pull that acts upon an object to form an interaction with another object.

This statement means that there is always a pair of forces acting on two interacting objects. The size of the forces on both objects are equal but the direction of the forces are opposite. E.g., an upward force pairs up with a downward force.

According to Newton’s third law of motion, whenever two objects interact with each other they exert forces upon each other.

For example; sitting on a chair…

When we sit on a chair our body exerts and downward force on the chair, the chair also exerts an upward force on the body. This relates to the forces being exerted upon both objects are equal and the direction of the forces are opposite. If the chair would not have exerted a force, the chair would collapse and we would not be able to sit on a chair. 

Isaac Newton’s law of motion also helps birds to fly. The bird’s wings exert a downward force on the air and the air exerts and equal and opposite force which pushes the bird upwards. This action-reaction combination helps birds to fly in the air. 

                                                                    Downward force

                                                               Upward force

Isaac Newton's early life and education.

Isaac Newton was born in the hamlet of Woolsthorpe, England on January 4, 1643. He was the only son of a successful farmer (also named Isaac Newton) who had died three months before he was born.


When he was three years old, his mother (Hannah Ayscough Newton) remarried a wealthy minister whom she went to live with, leaving young Newton with his maternal grandmother. This experience left an unforgettable imprint on Newton that later developed itself into an acute sense of insecurity.

It wasn’t until Hannah returned to Woolsthorpe in 1653 after the death of her second husband that Newton was granted attention from his mother, it was later discovered that this was a clue to his complex character. Newton’s childhood was anything but happy, and throughout his life he verged on emotional collapse, occasionally falling into violent and vindictive attacks against friend and foe.




Isaac Newton's education:


Beginning at the age of 12, Newton attended King's School, Grantham, where he was taught the basics, but no science or mathematics. With his mother's return to Woolsthorpe in 1653, 17 year old Newton was taken out of school to fulfill his birthright as a farmer. Newton happily failed in this field of work and returned to Kings's School at Grantham to prepare for entrance to Trinity College, Cambridge.


However before going to Trinity College, Newton finished his schooling at King's School as the top student. June, 1661 was the major turning point in Newton's life, this was when he left Woolsthorpe for Cambridge University. Here Newton entered a new world, one he could eventually call his own.

At the time when Newton was admitted to Trinity College, Cambridge, the college's teachings were based on those of Aristotle. In 1665 Newton discovered the generalised binomial theorem (a formula for finding any power of a binomial without multiplying at length), Newton began to develop a mathematical theory that later became infinitesimal calculus.

Soon after Newton had obtained his bachelor's degree in August 1665, the University closed down as a precaution against the Great Plague. Although Newton had been undistinguished as a Cambridge student, Newton's private studies at his home in Woolsthorpe over the next two years saw the development of his theories on calculus, optics and the law of gravitation. In 1667 he returned to cambridge as a fellow of Trinity




King's School, Grantham


Trinity University, Cambride 1665


Trinity University, Cambridge present day



Below is a simple explanation of Isaac Newton discovering gravity!