What is Newton's Second Law?

What Does Second law of Newton Mean

We explain what Newton's Second Law is, what its formula is and in which experiments or examples from everyday life it can be observed.

Newton's Second Law relates force, mass, and acceleration.

What is Newton's Second Law?

The second of the theoretical postulates made by the British scientist Sir Isaac Newton (1642-1727) based on the previous studies of Galileo Galilei and René Descartes is called Newton's Second Law or Fundamental Principle of Dynamics .

As his Law of Inertia , it was published in 1684 in his work Mathematical Principles of Natural Philosophy , one of the fundamental works of the modern study of physics . This law expresses, in the words of the scientist in Latin:

" Mutationem motus proportionalem esse vi motrici impressæ, & fieri secundum lineam straightm qua vis illa imprimitur "


" The change in motion is directly proportional to the printed motive force and occurs according to the straight line along which that force is printed ."

This means that the acceleration that a given body experiences is proportional to the force on it, which may or may not be constant. The essence of what is proposed by this second law has to do with the understanding that force is the cause of the change in motion and speed .

See also: What are the 3 Laws of Newton?

Newton's Second Law Formula

By the formula of Newton's Second Law, force, mass or acceleration can be calculated.

The fundamental formula of this Newtonian principle is:

F = ma

F is the force.

m is the mass of the body.

a is the acceleration.

Hence, the acceleration of an object can be calculated by applying the formula a = ƩF / m , with the exception that ƩF is the net force applied on the body. This means that if the force exerted on an object doubles, so will its acceleration ; while if the mass of the object is doubled, its acceleration will be half.

Newton's Second Law Experiments

A simple experiment to perform and that tests Newton's Second Law involves nothing more than a bat and several balls. The latter must be supported and immobile on a podium, and will be hit with the bat with the same amount of force.

The balls will be classified by approximate weight, to note how the same force exerted results in a greater or lesser acceleration depending on the mass of each ball.

Another possible experiment involves the same balls of different mass, which on this occasion will be dropped in a straight line (free fall) in such a way that only gravity acts on them . Since the latter is a constant force, the difference in mass is the only criterion for some to reach a greater acceleration, and therefore will hit the ground first .

Examples of Newton's Second Law

To move objects of greater mass, a greater force is required.

A simple example of the application of Newton's Second Law occurs when we push a heavy object . While the object is still, that is, with an acceleration equal to zero, we can set the object in motion by exerting a force on it that overcomes the inertia and gives it a certain acceleration.

If the object is extremely heavy or massive, that is, it has a great mass, we must exert greater force to increase its movement.

Another possible example is a car that accelerates its march, thanks to the force that the engine gives it . The greater the force exerted by the work of the engine, the faster the car will reach, that is, the greater the acceleration. A more massive car, for example a truck, will need more force to achieve the same acceleration than a lighter one.

Newton's other laws

Apart from Newton's Second Law, the scientist proposed two other fundamental principles, which are:

  • The Law of Inertia . Which reads: "Every body perseveres in its state of rest or of uniform rectilinear motion unless it is forced to change its state by forces impressed on it." This means that an object moving or at rest will not alter its state unless some kind of force is applied to it.
  • The Law of action and reaction . Which reads: "Every action corresponds to an equal reaction but in the opposite direction: it means that the mutual actions of two bodies are always equal and directed in the opposite direction." Which means that each force exerted on an object is opposed by a similar force exerted by it, in the opposite direction and of equal intensity.

Follow with: Law of Universal Gravitation

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