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The Laws of the Apple Guy: Newton’s Laws of Motion

Updated: Jan 29

Written by Evra Haspolat

Isaac Newton was a British physicist, mathematician, inventor, and philosopher. He has lots of works that are important to physics and other branches. First, with the book he published in 1687, Philisophiae Naturalis Principia Mathematica, in which he discussed the problems of mechanics and cosmology and then he showed people that although sunshine looked like it was bright white, it contained all of the color mixtures in his other book Opticks, which was published in 1704. Also, he is known best for contributing to the discovery of gravity since everybody knows that famous fake story of an apple falling to his head. He had found Newton’s Laws of Motion and has countless other works in physics and mathematics.

Newton’s laws of motion are 3 laws that explain the relationship between a physical object and the forces acting upon it. These laws are so important because they are the basics of physics so they can be seen used everywhere. These laws are:

  • The law of inertia

  • The law of force and acceleration

  • The law of action and reaction

Force: Force is an effect that can make a motionless object move, a moving object stay still or slow down, change its direction, and change its shape.

The Law of Inertia

“Every object moves in a straight line unless acted upon by a force”

This law states that a motionless object will continue to stay still and a moving object will continue to move. It means if there aren’t any external forces an object will stay still or continue moving at constant speed. So this law is objects that maintain the state of motion they are currently in.

Mass: Mass is a quantity that can be measured in kilograms and the amount of substance or energy. Mass can be mistaken with weight but weight is the magnitude of force that affects mass. The mass unit is kilograms while the weight unit is Newton.

The Law of Force and Acceleration: F=ma

“The acceleration of an object is directly proportional to the net force exerted and inversely proportional to the object’s mass.”

Mass’ definition comes from this law. Mass is net force division into acceleration. The first law, The Law of Inertia, is a specialized version of the second law: If a= 0 in the equation F=ma it’s gonna be F=0 and that means the object is not moving. Just like in The Law of Inertia.

Newton: According to SI capital N represents Newton which is the unit of force. Newton is used for showing the force's magnitude to change its acceleration. Also, the name Newton comes from who found this unit, Isaac Newton.

Weight and Gravitational Force:

  1. Weight: Weight is the force that affects the object by gravity. Weight is not a feature of an object. Mass is the amount of substance and weight is the force that affects a motionless object's mass by gravity. Capital G represents weight.

  2. Gravitational Force: g= 9.81m/sec2 (the equation of gravitational acceleration constant) Gravitational force is a power that is between two objects that have mass like Earth and the Sun. This force depends on two factors: Mass amount and the distance between the objects.

The Law of Action and Reaction

“For every action, there is an equal and opposite reaction.”

This law states that if there is a force towards an object, there will be a reaction towards the force in the same amount and opposite direction. So this means if Earth is pulling us down with 500N, we are pulling Earth up with 500N. There are lots of examples of this law:

  • If you put your feet on the wall when you’re swimming in a pool and push yourself, you would gain acceleration oppositely. Because the wall reacted with a force to you in the same amount but opposite direction.

  • When birds are flying their wings push the air downwards and the air pushes birds up.

  • We can also observe this on rockets and octopuses. The rocket pushes air down and air reacts by pushing the rocket up and like that the rocket starts to fly.

Octopuses’ movements in water are also an example.


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