Published in 1687 by Sir Isaac Newton, Philosophiae Naturalis Principia Mathematic, or, Mathematical Principles of Natural Philosophy, describes not only significant mathematical and physical interpretations needed to understand the motion of objects in our universe, but it formed the basis for all research in physics until his laws were updated in the early 20th century. In order to understand the laws, it is important to understand that they define the means by which motion changes, specifically the way in which those changes in motion are related to force and mass. Because we do not live in an environment free from any outside influences, it was necessary for Newton to build one so that an objects motion could be accurately studied before being altered by outside forces. This research led to the development of the three laws described below, published in his book
Newton’s 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.
This is usually referred to as inertia, or more officially the Law of Inertia, which states that an object not moving will stay still until an outside force acts upon it. Similarly, an object in motion will remain in motion until an outside force slows it down or stops it. While this may be difficult to comprehend, consider an object in motion inside a vacuum. If an object is thrown inside a vacuum, its initial velocity will not change because there is no air resistance to slow it down and no gravity to cause it to fall to the ground. Since we cannot build a vacuum of infinite space, the object will eventually strike the opposite side of the container and stop.
Newton’s Second Law of Motion
The acceleration produced by a particular force acting on a body is directly proportional to the magnitude of the force and inversely proportional to the mass of the body.
Many people will recognize the equation F = m * a, or Force = mass times acceleration. This means that the amount of force generated is directly porportional to the mass of the object multiplied by its acceleration. Conversely, if you know how much force you are applying and the mass of the object, you can determine how fast the object will accelerate. Please note that friction is not taken into account in this equation.
Newton’s 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.
This law takes any object, its mass and interprets it as force. This means that if you were to attempt to push a car, you would need to overcome the amount of force the car is exerting on you. Of course this is a figurative force, but in order to overcome friction and state it in an equation logically it needs to be considered a real one.
The three laws of motion Newton postulated over three hundred years ago served the physics community well until around the time of Einstein when other physicists went beyond his research with more advanced techniques. Still, the three laws remain valid today and are a worldwide standard when beginning any education on physics.
Sources
about.com
wikipedia.com
