Transcript Newton`s three laws of motion

Newton’s Three Laws
of Motion
BIXUAN SANG
X U YA N
WEIMO XU
TA O R A N X U E
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,
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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