It is known under the term Newton's Third Law a principle that states that, if a body A performs an action on a body B, the latter body will exert a similar action on body A in the opposite direction. Newton's laws of motion or also called Newton's Laws, are three precepts through which many of the problems that arise within classical mechanics can be explained, especially those that are related to the displacements of bodies..
This law is also known as the principle of action and reaction and is the representation of a part of symmetry within nature; forces generally occur in pairs and it is not possible for a body to exert an energy on another body, without the first having experienced an energy first. Within Newton's laws of action and reaction, it can be said that the force that is applied is the action, while the force that is presented as a consequence of the previous one is the reaction.
What is Newton's third law?
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“When one object exerts a certain force on another, the object that receives said energy will exert a force in the opposite direction, but of equal magnitude to the first object. When an interaction of any kind occurs, two forces of action and reaction also occur, their magnitude being similar, but with totally opposite directions. "
Background to Newton's third law
From ancient times, until even the Middle Ages, the theories of movement that had greater acceptance by the scientific community were those proposed by Aristotle, this scientist considered that movement was a variation from the state of rest that required a cause, classifying the others in violent movements and natural movements.
According to Aristotle the cosmos was a sphere of great dimensions, but it was limited by the sphere of fixed stars. For its part, the earth was in the center of the cosmos and was surrounded by structures of fire, water and air in the shape of a sphere.
This theory indicates that each substance or body had a natural site and a natural movement that was related to that place, to which it was generally directed in a straight line. Being in the place it was possible that it was at rest, for that reason it was that the fire is considered light, since its natural posture was above, while the earth had a natural place below and therefore seems heavy.
Examples of Newton's third law
To better explain what Newton's third law postulates, the following examples are proposed:
- A person who is climbing a mountain exerts a force on the rocks, this will cause a pulling force to be produced in the individual, which will allow him to climb through the rocks of the mountain.
- Another example can be when climbing a ladder, since when an individual begins to climb them, it is necessary that they first put one foot on the step and push, the step must exert a similar force and in the opposite direction on the foot to prevent it from breaking If the force that the foot exerts on the step is greater, so will the reaction against the foot.
Newton's Law Formulas
The formulas for Newton's laws are as follows:
First Law
The first law indicates that for a body that is in a state of rest or moving in a straight line to modify its trajectory, a force must be exerted on it. In the same way it is indicated that in both cases the reaction force applied to the body is zero. For this reason, for this law it is established as a formula that the sum of the forces will have as a result 0. ΣF = 0
Second law
For its part, the second law establishes as a formula that force is equal to mass multiplied by acceleration. F = ma
Third Law
The third law establishes as a formula that the force exerted on one body is equal to the reaction force that acts on the second body. F1 = F2
