What are the laws of Motion? According to Wikipedia – “Newton’s laws of motion are three basic laws of classical mechanics that describe the relationship between the motion of an object and the forces acting on it. These laws can be paraphrased as follows:
- A body remains at rest, or in motion at a constant speed in a straight line, unless acted upon by a force.
- When a body is acted upon by a force, the time rate of change of its momentum equals the force.
- If two bodies exert forces on each other, these forces have the same magnitude but opposite directions.”
These three laws of motion were first stated by Sir Issac Newton. It was published in 1687 in his Mathematical Principles of Natural Philosophy. He used these laws for investigation and explanation of the motion of many physical objects and systems. This laid the foundation of classical mechanics.
Do you know – Newton’s law of motion when combined with his laws of gravity, allows physicists to predict how planets, moons, and other objects orbit through the solar system. It is needed because it is one of the most important parts when planning for space travel.
The concepts invoked in Newton’s laws of motion were mass, velocity, momentum, and force. After Newton’s time too, the content of Newtonian physics was developed further.
Isaac Newton: The mathematician who invented laws of motion.
First Law of Motion
“Every body continues in its state of rest, or of uniform motion in a straight line unless it is compelled to change that state by forces impressed upon it.” – Issac Newton
Newton’s first law states the principle of inertia. It expresses that the natural behavior of a body is to move in a straight line and at a constant speed. If there are no outside influences present, a body’s motion preserves the status quo.
Second Law of Motion
“The change of motion of an object is proportional to the force impressed, and is made in the direction of the straight line in which the force is impressed.” – Issac Newton
By “motion”, what Newton meant was the quantity that is now known as momentum. It depends upon the amount of matter contained in a body, the speed at which that body is moving, and the direction in which it is moving. In modern terms, the momentum of a body is the product of its mass and its velocity.
Third Law of Motion
“To every action, there is always opposed an equal reaction; or, the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.” – Issac Newton
The most common paraphrases of the third law will be “action equals reaction.” It has contributed to a problem that has caused great and continual trouble to generations of students, that is, the “action” and “reaction” apply to different bodies. For example, consider a notebook at rest on a table. The Earth’s gravity will pull down upon the book. The “reaction” to that “action” is not the force that is supported by the table holding up the book, but the gravitational pull of the book acting on the Earth.