BIXUAN SANG XU YAN WEIMO XU TAORAN XUE Newton’s Three Laws of Motion.

BIXUAN SANG XU YAN

WEIMO XUTAORAN XUE

Newton’s Three Laws of Motion

Introduction

Despite of the discovery of the law of gravity, Isaac Newton also discovered the three laws of motion. He published them in his book “Philosophiae Naturalis Principia Mathematica” (mathematic principles of natural philosophy) in 1687.

Nowadays, these laws are known as Newton’s Laws of Motion and describe the motion of all objects on the scale we experience in our everyday lives.

We have already learned Newton’s three laws and applications in class. The world is full of motions, and Newton’s laws of motion are contained in our daily life. This aroused our interests and makes us want to explore further.

Newton’s First Law of Motion

Isaac Newton first introduced his three law of motion to the society in 1686. The first law of motion clearly demonstrated that every object will remain at rest or in uniform motion in a straight line unless an external force act on the object and compel it to change its state. This law is often referred to as the law of inertia. The main point here is that the object will maintain a constant velocity if there is no net force acting on an object.

Newton’s First Law of Motion

Also, if the velocity is zero, then the object will remain at rest. The amount of the change in velocity is determined by Newton's second law of motion. Newton’s first law is widely applied in our daily life. The motion of a rock falling down through air, or a rocket being launched up into the atmosphere are examples.

Newton’s Second Law of Motion

When we talk about Newton's Second Law of Motion-Force and Acceleration, the first thing comes up is “F=ma”. Newton’s second law of motion is usually related to the movement of objects for which all existing forces are not balanced. There are several aspects that can be used to describe the Newton Second Law. The first one is causality. Force is the cause of the acceleration. If there is no force on the object there is no acceleration. Second, force and acceleration is both vector. The direction of the object’s acceleration is affected by the direct of the force on the object.

Newton’s Second Law of Motion

The third one is instantaneity, if the force on the object changes instantly (mass remain the same), the acceleration must change at the same time. Also we should notice that we cannot say F has a direct proportion relationship with a because the total force indicate the acceleration. We should aware that F=ma is a vector equation and all the positive direction will count in positive value, otherwise use the negative value. Normally we say that the direction of the acceleration will be the positive direction.

Newton’s Third Law of Motion

Newton’s Third Law of Motion, also know as action-reaction law, states that “Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first”. It means that all forces are interactions between different bodies. 　F=-F' When two objects interact with each other, they exert forces upon each other.

Newton’s Third Law of Motion

This law can be illustrated from some examples in our life. If a flying bird doing its motion by its wings downwards, the air pushes the bird upwards because for every action, there is an equal and opposite reaction.

Einstein’s Theory of Motion

In Newtonian Mechanics, the space and time are absolute, universal and independent of motion of bodies in space.

Albert Einstein treated matter and energy as exchangeable. Theory of Relativity revolutionized scientific thought with new conceptions of time, space, mass, motion, and gravitation. (Tesla Memorial Society of New York)

Only relative motion can be measured!!! E=mc² (energy equals mass times the

velocity of light squared) we also leaned this in class.

From then, Newton’s work has been improved. Now, motion is relative to Time and Position. But Newton’s Laws of Motion is the fundamental. These theories have changed our understanding of the universe.

References

Newton's three laws of motion, photo, Nir Shaviv, sciencebits.com

Albert Einstein (1879 - 1955), Dr. Ljubo Vujovic, Secretary General, Tesla Memorial Society of New York, http://www.teslasociety.com/einstein.htm

Tom Benson. Newton’s First Law. National Aeronautics and Space Administration. Web.Sep 10 2010.

http://en.wikipedia.org/wiki/Newton%27s_laws_of_motion#Newton.27s_third_law

http://www.physicsclassroom.com/class/newtlaws/u2l4a.cfm