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

## What is Newton's Second Law?

Newton's Second Law or Fundamental Principle of Dynamics is called 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.

Just like 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 rectam qua vis illa imprimitur*”

What it means:

“**The change in motion is directly proportional to the driving force printed and occurs along the straight line along which that force is printed** ”.

This means that the acceleration that a given body experiences is proportional to the force exerted 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 change in motion and speed**.

See also: What are Newton's 3 Laws?

## Newton's Second Law Formula

The fundamental formula of this Newtonian principle is:

**F = ma**

**F** It is the force.

** m** is the mass of the body.

** to** 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 doubles, its acceleration will be half.

## Experiments on Newton's Second Law

A simple experiment to perform that proves Newton's Second Law involves nothing more than a bat and several balls. The latter must be supported and motionless 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 masses, 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 they will hit the ground first.

## Examples of Newton's Second Law

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

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

Another possible example is **a car that accelerates its pace, thanks to the force that the engine gives it**. The greater the force exerted by the work of the engine, the greater the speed 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 uniform rectilinear motion unless it is forced to change its state by forces imposed on it.” This means that an object moving or at rest will not alter its state unless some type of force is applied to it.**The Law of action and reaction**Which reads: “To every action there corresponds an equal reaction but in the opposite direction: it means that the mutual actions of two bodies are always equal and directed in opposite directions.” 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.

Continue with: Law of Universal Gravitation

#### References

- “Newton's Laws” on Wikipedia.
- “What is Newton's Second Law?” at Khan Academy.
- “Newton's Laws” in Hyperphysics.
- “Newton's Laws” at the Scientific Computing Center of Andalusia.
- “Newton's Second Law” in FisicaLAB.
- “Newton's laws of motion” in The Encyclopaedia Britannica.