Newton’s first law


The first law of Newton also known in the field of science as the law of inertia , is one of the most important aspects to take into account when we are referring to the movement .


What is Newton’s first law?

Newton’s first law tells us that every body tends to maintain the state in which it is found, whether of rest or of uniform motion and in a straight line , unless it is forced to change its direction or its state by external forces .

  • What is Newton’s first law?
  • What is your name
  • Who proposed it
  • History
  • Statement of Newton’s first law
  • features
  • Formula
  • Target
  • Explanation
  • Newton’s First Law Applications
  • Experiment
  • Examples
  • Conclution

What is Newton’s first law?

It consists of a statement that establishes that there must be a net external cause or force to achieve a change in speed , either in the magnitude or in the direction of a certain object. Newton’s first law is that if the net force exerted on an object is zero then that object will also have zero acceleration , which does not mean that the object is in a state of rest, but that the speed is constant .


What is your name

Newton’s first law is also known as the law of inertia .

Who proposed it

Newton’s first law was proposed by Newton himself but he was not the first to intuit that bodies were driven to maintain their state if there was no environmental force acting on them, and among these scientists who also referred to them we find precedents in Leonardo, Galileo , Descartes or Hooke .


The history of Newton’s first law is based on the works of Galileo and Johannes Kepler , and through them it was that Isaac Newton was able to develop the theory about the movements of bodies , and it was this theory that was responsible for giving rise to the three laws.

Statement of Newton’s first law

The main statement that tells us about Newton’s first law is the following: “Every body continues in its state of rest or of uniform motion in a straight line , unless it is forced to change that state by forces acting on it.”


The main characteristics of Newton’s first law are as follows:

  • Bodies have inertia if no force is applied to them.
  • Bodies retain their state of rest or of uniform rectilinear motion if there are no forces that produce a change.
  • It is widely used in mechanical and thermal inertia .
  • All bodies that are at rest tend to remain at rest.
  • The bodies are reluctant to change their state .
  • The greater the mass of the body, the more inertia it will have.
  • Bodies tend to resist physical change .


The formula to be able to use Newton’s first law is the following:

∑F = 0 ⇔ = dv / dt = 0


The objective of Newton’s first law is to show that all matter cannot be modified by itself and that it needs an external force to be able to vary the speed. It also teaches us that a body that is in motion will also stay in this way if no friction or friction is applied to it .


Newton’s first law tells us that a body does not have the ability to change its initial state by itself , whether this body is in a state of rest or has a uniform rectilinear motion, unless a force is applied net about it. Newton considered when he developed the formula that all bodies that are in motion are constantly subjected to friction or friction forces , which progressively slows them down . The fact that an object is in a state of rest, It does not indicate that there is no force that can act on it, this means that the forces that are acting on the object are in equilibrium . The law also tells us about bodies in rectilinear motion , which move without acceleration with constant motion , in other words they have a balance of forces.

Newton’s First Law Applications

Newton’s first law can be used in the constancy of speeds in automobiles, it is also applied in solving problems in classical mechanics .



  • A coin.
  • A glass.
  • A card or card.
  • A bottle.
  • A circle (made with paper and tape).
  • A box or a book.


  • Lay the card flat on top of the glass.
  • Put the coin on top of the card.
  • Hit the card hard and sharply.


When the card is struck, no force is exerted on the coin. According to Newton’s first law, if the net force acting on an object is zero then the object will remain at rest if it was in this way or in motion.

As the coin was still on top of the card and as no force was applied to it, when removing the card the coin fell into the glass, because the only force acting on it was gravity.


Some examples of Newton’s first law are as follows:

  • car that must brake hard.
  • An attempt to push a car that is stationary.
  • The athlete who cannot stop in a single instant, but must stop little by little.
  • The pedaling of a bicycle that allows you to move forward without pedaling when stopped.
  • The roller coasters that climb slopes thanks to the inertia produced by the previous descent.


In conclusion, we know that Newton’s first law or Law of inertia tells us that, if no other acts on a body , the first will keep moving in a straight line with a constant speed . This law helps us to define inertial reference systems , which serve as a reference for observation of a body on which no force acts.

The truth is that it is impossible for us to find an inertial reference system, because there is always some kind of force that acts on bodies, but we can find a reference system in which the problem we are studying can be treated as if we were in an inertial system.

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