# What are Newton’s laws?

Newton’s laws are three principles that explain how bodies move when acted on by forces with a constant speed. They have been used to describe the movement of man-made objects, such as modes of transportation or machinery, as well as phenomena of universal gravitation like planetary motion. Since they were first proposed, Newton’s Laws have helped explain facts related to classical mechanics and physics.

## Who was Newton?

Isaac Newton was an English physicist, mathematician, philosopher, and theologian who became a leader in the sciences through his important contributions, such as the principle of universal gravitation, establishing the foundations of classical mechanics, his studies on the nature of light and optics, and the development of calculus, among other things.

## What terms are related to Newton’s laws in order to help understand them?

To understand Newton’s laws, we must first know three essential concepts that give meaning to the English scientist’s theories.

• Force: a specific action that allows an object to move or even change its shape. That action can be lifting, pulling, pushing, or dragging a body.
• Movement: this refers to an object’s change in position over time, starting from a reference point.
• Acceleration: the change in speed that a moving body or object can experience.

Another concept that Newton used to develop his laws was that of mass, defining it as a quantity of matter.” Thus, movement is the result of mass times the velocity applied to it.

## What are Newton’s laws?

Newton’s laws have served to explain and describe the movement of bodies subjected to a force and a specific acceleration. These principles were postulates in his 1687 work Mathematical Principles of Natural Philosophy. The laws’ approach was based on quantitative observations and experiments with which the scientist made predictions.

These are three fundamental laws that are considered the most important in classical mechanics since they respond to all types of movements. They are: the law of inertia, the relationship between force and acceleration, and the law of action and reaction, all posed as mathematical formulas.

1. Newton’s First Law or the law of inertia

A body remains at rest, or in motion at a constant speed in a straight line, unless acted upon by a force.

This law of motion states that a body cannot change its initial state of rest or of movement in a straight line at a constant speed if one or more external forces are not applied to it. The concept of inertia was initially proposed by Galileo Galilei, which is why Newton is only credited with the publication of the principle and not its authorship.

This law contradicts the Aristotelian principle that says that a body can only move if a sustained force is applied to it since the Newtonian law states that an object in motion or even at rest does not change state unless some kind of external force is applied to it.
2. Newton’s Second Law, or the fundamental law of dynamics

When a force acts on an object, the object is set in motion, accelerates, decelerates, or changes its trajectory.

This law states that the net force applied to an object is directly proportional to the acceleration that it acquires in its trajectory. That is, a body accelerates when a force is applied to it to move it. If a greater net force is applied to it, the acceleration of the body will increase.
3. Newton’s Third Law, or the principle of action and reaction

For every action, there is an equal and opposite reaction: that is, the mutual actions of two bodies are always equal and directed in opposite directions.

This law states that every action generates a reaction of equal intensity but in the opposite direction. This means that whenever one object exerts a force on another, the latter will return a force of equal magnitude but in the opposite direction to the first.

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