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Encyclopedia > Newton's Laws of Motion
Newton's First and Second laws, in Latin, from the original 1687 edition of the Principia Mathematica.
Newton's First and Second laws, in Latin, from the original 1687 edition of the Principia Mathematica.
Classical mechanics
History of ...
Formulations
Newtonian mechanics
Lagrangian mechanics
Hamiltonian mechanics
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Newton's laws of motion are three physical laws which provide relationships between the forces acting on a body and the motion of the body. They were first compiled by Sir Isaac Newton in his work Philosophiae Naturalis Principia Mathematica (1687). The laws form the basis for classical mechanics and Newton himself used them to explain many results concerning the motion of physical objects. In the third volume of the text, Newton showed that these laws of motion, combined with his law of universal gravitation, explained Kepler's laws of planetary motion. Image File history File links Newtons_laws_in_latin. ... Image File history File links Newtons_laws_in_latin. ... For Whitehead and Russells axiomatic work on mathematics, see Principia Mathematica. ... Classical mechanics (commonly confused with Newtonian mechanics, which is a subfield thereof) is used for describing the motion of macroscopic objects, from projectiles to parts of machinery, as well as astronomical objects, such as spacecraft, planets, stars, and galaxies. ... Newtons First and Second laws, in Latin, from the original 1687 edition of the Principia Mathematica. ... The Greeks, and Aristotle in particular, were the first to propose that there are abstract principles governing nature. ... This article is about the idea of space. ... This article is about the concept of time. ... For other uses, see Mass (disambiguation). ... For other uses, see Force (disambiguation). ... This article is about momentum in physics. ... Lagrangian mechanics is a re-formulation of classical mechanics that combines conservation of momentum with conservation of energy. ... Hamiltonian mechanics is a re-formulation of classical mechanics that was invented in 1833 by William Rowan Hamilton. ... Applied mechanics, also known as theoretical and applied mechanics, is a branch of the physical sciences and the practical application of mechanics. ... Celestial mechanics is a division of astronomy dealing with the motions and gravitational effects of celestial objects. ... Continuum mechanics is a branch of physics (specifically mechanics) that deals with continuous matter, including both solids and fluids (i. ... See also list of optical topics. ... Statistical mechanics is the application of probability theory, which includes mathematical tools for dealing with large populations, to the field of mechanics, which is concerned with the motion of particles or objects when subjected to a force. ... Galileo redirects here. ... Kepler redirects here. ... Sir Isaac Newton FRS (4 January 1643 – 31 March 1727) [ OS: 25 December 1642 – 20 March 1727][1] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist. ... Pierre-Simon, marquis de Laplace (March 23, 1749 - March 5, 1827) was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy. ... For other persons named William Hamilton, see William Hamilton (disambiguation). ... Jean le Rond dAlembert, pastel by Maurice Quentin de La Tour Jean le Rond dAlembert (November 16, 1717 – October 29, 1783) was a French mathematician, mechanician, physicist and philosopher. ... Augustin Louis Cauchy (August 21, 1789 – May 23, 1857) was a French mathematician. ... Joseph-Louis, comte de Lagrange (January 25, 1736 Turin, Kingdom of Sardinia - April 10, 1813 Paris) was an Italian-French mathematician and astronomer who made important contributions to all fields of analysis and number theory and to classical and celestial mechanics as arguably the greatest mathematician of the 18th century. ... Euler redirects here. ... In the article vector quantities are written in bold whereas scalar ones are in italics. ... For a list of set rules, see Laws of science. ... In mathematics and statistics, a direct relationship is a positive relationship between two variables in which they both increase or decrease in conjunction. ... For other uses, see Force (disambiguation). ... A physical body is an object which can be described by the theories of classical mechanics, or quantum mechanics, and experimented upon by physical instruments. ... This article or section is in need of attention from an expert on the subject. ... Sir Isaac Newton FRS (4 January 1643 – 31 March 1727) [ OS: 25 December 1642 – 20 March 1727][1] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist. ... Newtons own copy of his Principia, with handwritten corrections for the second edition. ... Events March 19 - The men under explorer Robert Cavelier de La Salle murder him while searching for the mouth of the Mississippi River. ... Classical mechanics (commonly confused with Newtonian mechanics, which is a subfield thereof) is used for describing the motion of macroscopic objects, from projectiles to parts of machinery, as well as astronomical objects, such as spacecraft, planets, stars, and galaxies. ... Isaac Newtons theory of universal gravitation (part of classical mechanics) states the following: Every single point mass attracts every other point mass by a force pointing along the line combining the two. ... Illustration of Keplers three laws with two planetary orbits. ...


Traditional brief statements of the three laws:

  1. A physical body will remain at rest, or continue to move at a constant velocity, unless an outside net force acts upon it.
  2. Rate of change of momentum is proportional to the resultant force producing it and takes place in the direction of that force.[1][2][3][4][5]
  3. To every action there is an equal and opposite reaction.

Contents

This article is about velocity in physics. ... This article is about vectors. ... This article is about momentum in physics. ... For other uses, see Force (disambiguation). ...

The three laws in detail

Newton's laws of motion describe the acceleration of massive particles. In modern language, the laws may be stated as: Acceleration is the time rate of change of velocity and/or direction, and at any point on a velocity-time graph, it is given by the slope of the tangent to the curve at that point. ... For other uses, see Mass (disambiguation). ...

First law
If no net force acts on a particle, then it is possible to select a set of reference frames, called inertial reference frames, observed from which the particle moves without any change in velocity. This law is often simplified into the sentence "An object will stay at rest or continue at a constant velocity unless acted upon by an external unbalanced force".
Second law
Observed from an inertial reference frame, the net force on a particle is proportional to the time rate of change of its linear momentum: F = d ( mv ) / dt. Momentum mv is the product of mass and velocity. This law is often stated as F = m a (the net force on an object is equal to the mass of the object multiplied by its acceleration), but this approximation to the law is accurate only for speeds much less than the speed of light. An important point is that force and momentum are vector quantities and that the resultant force is found from all the forces present by vector addition.
Third law
Whenever a particle A exerts a force on another particle B, B simultaneously exerts a force on A with the same magnitude in the opposite direction. The strong form of the law further postulates that these two forces act along the same line. This law is often simplified into the sentence "Every action has an equal and opposite reaction".

In the given interpretation mass, acceleration, and, most importantly, force are assumed to be externally defined quantities. This is the most common, but not the only interpretation: one can consider the laws to be a definition of these quantities. Notice that the second law only holds when the observation is made from an inertial reference frame, and since an inertial reference frame is defined by the first law, asking a proof of the first law from the second law is a logical fallacy. For other uses, see Force (disambiguation). ... A frame of reference in physics is a set of axes which enable an observer to measure the aspect, position and motion of all points in a system relative to the reference frame. ... In physics, an inertial frame of reference, or inertial frame for short (also descibed as absolute frame of reference), is a frame of reference in which the observers move without the influence of any accelerating or decelerating force. ... This article is about velocity in physics. ... This article is about momentum in physics. ... A line showing the speed of light on a scale model of Earth and the Moon, taking about 1â…“ seconds to traverse that distance. ... This article is about vectors that have a particular relation to the spatial coordinates. ... This article is about vectors that have a particular relation to the spatial coordinates. ... It has been suggested that this article or section be merged into Fallacy. ...


Newton's first law: law of inertia

Lex I: Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis cogitur statum illum mutare.


Every body perseveres in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed.[6]

This law is also called the law of inertia. This article is about inertia as it applies to local motion. ...


This is often paraphrased as "zero net force implies zero acceleration", but this is an over-simplification. As formulated by Newton, the first law is more than a special case of the second law. Newton arranged his laws in hierarchical order for good reason (for example, see Gailili & Tseitlin[7], or Woodhouse[8]). The significance of the first law is to establish frames of reference for which the other laws are applicable, such frames being called inertial frames. A frame of reference in physics is a set of axes which enable an observer to measure the aspect, position and motion of all points in a system relative to the reference frame. ... In physics, an inertial frame of reference, or inertial frame for short (also descibed as absolute frame of reference), is a frame of reference in which the observers move without the influence of any accelerating or decelerating force. ...


To understand why the laws are restricted to inertial frames, consider a ball at rest within an accelerating body: an airplane on a runway will suffice for this example. From the perspective of anyone within the airplane (that is, from the airplane's frame of reference when put in technical terms) the ball will appear to move backwards as the plane accelerates forwards (the same feeling as being pushed back into your seat as the plane accelerates). This motion appears to contradict Newton's second law as, from the point of view of the passengers, there appears to be no force acting on the ball that would cause it to move. The reason why there is in fact no contradiction to the second law is because Newton's second law (without modification) is not applicable in this situation: Newton's first law does not apply because the stationary ball does not remain stationary. Thus, it is important to establish whether the various laws are applicable or not, inasmuch as they are not applicable in all situations.[9] To summarize:[8]

There is a class of frames of reference (called inertial frames) relative to which the motion of a particle not subject to forces is a straight line.

The net force on an object is the vector sum of all the forces acting on the object. Newton's first law says that if this sum is zero, the state of motion of the object does not change. Essentially, it makes the following two points: A vector in physics and engineering typically refers to a quantity that has close relationship to the spatial coordinates, informally described as an object with a magnitude and a direction. The word vector is also now used for more general concepts (see also vector and generalizations below), but in this...

  • An object that is not moving will not move until a net force acts upon it.
  • An object that is in motion will not change its velocity (accelerate) until a net force acts upon it.

The first point seems relatively obvious to most people, but the second may take some thinking through, because we have no experience in every-day life of things that keep moving forever (except celestial bodies). If one slides a hockey puck along a table, it doesn't move forever, it slows and eventually comes to a stop. But according to Newton's laws, this is because a force is acting on the hockey puck and, sure enough, there is frictional force between the table and the puck, and that frictional force is in the direction opposite the movement. It is this force which causes the object to slow to a stop. In the absence of such a force, as approximated by an air hockey table or ice rink, the puck's motion would not slow. Newton's first law is just a restatement of what Galileo had already described and Newton gave credit to Galileo. It differs from Aristotle's view that all objects have a natural place in the universe. Aristotle believed that heavy objects like rocks wanted to be at rest on the Earth and that light objects like smoke wanted to be at rest in the sky and the stars wanted to remain in the heavens. This article is about velocity in physics. ... Galileo can refer to: Galileo Galilei, astronomer, philosopher, and physicist (1564 - 1642) the Galileo spacecraft, a NASA space probe that visited Jupiter and its moons the Galileo positioning system Life of Galileo, a play by Bertolt Brecht Galileo (1975) - screen adaptation of the play Life of Galileo by Bertolt Brecht... For other uses, see Aristotle (disambiguation). ...


However, a key difference between Galileo's idea and Aristotle's is that Galileo realized that force acting on a body determines acceleration, not velocity. This insight leads to Newton's First Law—no force means no acceleration, and hence the body will maintain its velocity.


The Law of Inertia apparently occurred to several different natural philosophers and scientists independently. The inertia of motion was described in the 3rd century BC by the Chinese philosopher Mo Tzu, and in the 11th century by the Muslim scientists, Alhazen[10] and Avicenna.[11] The 17th century philosopher René Descartes also formulated the law, although he did not perform any experiments to confirm it. Mozi (Chinese: ; pinyin: ; Wade-Giles: Mo Tzu, Lat. ... In the history of science, Islamic science refers to the science developed under the Islamic civilisation between the 8th and 15th centuries (the Islamic Golden Age). ... (Arabic: أبو علي الحسن بن الحسن بن الهيثم, Latinized: Alhacen or (deprecated) Alhazen) (965 – 1039), was an Arab[1] Muslim polymath[2][3] who made significant contributions to the principles of optics, as well as to anatomy, astronomy, engineering, mathematics, medicine, ophthalmology, philosophy, physics, psychology, visual perception, and to science in general with his introduction of the... (Persian: ابن سينا) (c. ... Descartes redirects here. ...


There are no perfect demonstrations of the law, as friction usually causes a force to act on a moving body, and even in outer space gravitational forces act and cannot be shielded against, but the law serves to emphasize the elementary causes of changes in an object's state of motion. For other uses, see Friction (disambiguation). ...


Newton's second law: law of resultant force

Lex II: Mutationem motus proportionalem esse vi motrici impressae, et fieri secundum lineam rectam qua vis illa imprimitur.


The rate of change of momentum of a body is proportional to the resultant force acting on the body and is in the same direction.

In Motte's 1729 translation (from Newton's Latin), the second law of motion reads:[12]

LAW II: The alteration of motion is ever proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed. — If a force generates a motion, a double force will generate double the motion, a triple force triple the motion, whether that force be impressed altogether and at once, or gradually and successively. And this motion (being always directed the same way with the generating force), if the body moved before, is added to or subtracted from the former motion, according as they directly conspire with or are directly contrary to each other; or obliquely joined, when they are oblique, so as to produce a new motion compounded from the determination of both.

Using modern symbolic notation, Newton's second law can be written as a vector differential equation: This article is about vectors that have a particular relation to the spatial coordinates. ... Visualization of airflow into a duct modelled using the Navier-Stokes equations, a set of partial differential equations. ...

vec F_{net} = {mathrm{d}(m vec v) over mathrm{d}t}

where:

vec F! is the force vector
m! is mass
vec v! is the velocity vector
t! is time.

The product of the mass and velocity is the momentum of the object (which Newton himself called "quantity of motion"). It should be noted that, as is consistent with the law of inertia, the time derivative of the momentum is non-zero when the momentum changes direction, even if there is no change in its magnitude. See time derivative.[13] For other uses, see Force (disambiguation). ... For other uses, see Mass (disambiguation). ... This article is about velocity in physics. ... This article is about the concept of time. ... For other uses, see Mass (disambiguation). ... This article is about velocity in physics. ... This article is about momentum in physics. ... A time derivative is a derivative of a function with respect to time, t. ...


If the mass of the object in question is constant this differential equation can be rewritten as:

vec F = m vec a

where:

vec a! = frac{mathrm{d} vec v}{mathrm{d}t} is the acceleration.

A verbal equivalent of this is "the acceleration of an object is proportional to the force applied, and inversely proportional to the mass of the object". If momentum varies nonlinearly with velocity (as it does for high velocities—see special relativity), then this last version is not accurate. Acceleration is the time rate of change of velocity and/or direction, and at any point on a velocity-time graph, it is given by the slope of the tangent to the curve at that point. ... For a less technical and generally accessible introduction to the topic, see Introduction to special relativity. ...


Impulse

The term impulse is closely related to the second law, and historically speaking is closer to the original meaning of the law.[14]The meaning of an impulse is as follows:[15][16] For other uses, see Impulse (disambiguation). ...

An impulse occurs when a force F acts over an interval of time Δt and is given by int_{Delta t} F  dt .

The words motive force were used by Newton to describe "impulse" and motion to describe momentum; consequently, a historically closer reading of the second law describes the relation between impulse and change of momentum. That is, a mathematical rendering of the original wording resembles a finite difference version of the second law, rather than a differential version. A finite difference is a mathematical expression of the form f(x + b) − f(x + a). ...


The analysis of collisions and impacts uses the impulse concept.[17]


Relativity

Taking special relativity into consideration, the law of resultant force can be put in terms of acceleration as follows:[18] For a less technical and generally accessible introduction to the topic, see Introduction to special relativity. ...

 vec F = frac {d vec {p} }{d t} = frac {d m vec {v} }{d t}
= m frac {d vec {v} }{d t} + frac {d m }{d t}vec {v}
= m frac {d vec {v} }{d t} + frac{1}{c_0^2} frac {d E }{d t}vec {v}
= m frac {d vec {v} }{d t} + frac { left(vec {F} cdot vec {v}  right)}{c_0^2}vec {v} ,

where the famous result for the energy E = m c02 is used with c0 = speed of light in free space, and the relation A line showing the speed of light on a scale model of Earth and the Moon, taking about 1â…“ seconds to traverse that distance. ... In physics, free space is a concept of electromagnetic theory, corresponding roughly to the vacuum, the baseline state of the electromagnetic field, or the replacement for the electromagnetic aether. ...

frac {d E }{dt} = left( vec F cdot vec v  right)  ,

describes the work done by the force per unit time. Here ( F • v ) is the vector dot product. In mathematics, the dot product, also known as the scalar product, is a binary operation which takes two vectors over the real numbers R and returns a real-valued scalar quantity. ...


This equation can be rearranged to form the modified force law:

 m frac {d vec v }{dt} = vec F - frac {( vec F cdot vec v  )} {c_0^2} vec v  ,

which shows that although the change of momentum is in the direction of the force, in general the acceleration of the mass is not in the direction of the force. However, when the speed of the moving body is much lower than the speed of light, the equation above reduces to the familiar F = ma.


Open systems

So-called variable mass systems that are not closed systems, like a rocket burning fuel and ejecting spent gases, can not be directly treated by making mass a function of time in the second law.[19] The reasoning, given in An Introduction to Mechanics by Kleppner and Kolenkow and other modern texts, is excerpted here: In thermodynamics, a closed system, as contrasted with an isolated system, can exchange heat and work, but not matter, with its surroundings. ...

Newton's second law applies fundamentally to particles. In classical mechanics, particles by definition have constant mass. In case of well-defined systems of particles, Newton's law can be extended by integrating over all the particles in the system. In this case, we have to refer all vectors to the center of mass. Applying the second law to extended objects implicitly assumes the object to be a well-defined collection of particles. However, 'variable mass' systems like a rocket or a leaking bucket do not consist of a set number of particles. They are not well-defined systems. Therefore Newton's second law can not be applied to them directly. The naïve application of F = dp/dt will usually result in wrong answers in such cases. However, applying the conservation of momentum to a complete system (such as a rocket and fuel, or a bucket and leaked water) will give unambiguously correct answers.

Newton's third law: law of reciprocal actions

Lex III: Actioni contrariam semper et æqualem esse reactionem: sive corporum duorum actiones in se mutuo semper esse æquales et in partes contrarias dirigi.


All forces occur in pairs, and these two forces are equal in magnitude and opposite in direction.

In other words "For every force there is an equal, but opposite, force".

Newton's third law. The skaters' forces on each other are equal in magnitude, and in opposite directions
Newton's third law. The skaters' forces on each other are equal in magnitude, and in opposite directions

A more direct translation is:

LAW III: 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. — Whatever draws or presses another is as much drawn or pressed by that other. If you press a stone with your finger, the finger is also pressed by the stone. If a horse draws a stone tied to a rope, the horse (if I may so say) will be equally drawn back towards the stone: for the distended rope, by the same endeavour to relax or unbend itself, will draw the horse as much towards the stone, as it does the stone towards the horse, and will obstruct the progress of the one as much as it advances that of the other. If a body impinges upon another, and by its force changes the motion of the other, that body also (because of the equality of the mutual pressure) will undergo an equal change, in its own motion, toward the contrary part. The changes made by these actions are equal, not in the velocities but in the motions of the bodies; that is to say, if the bodies are not hindered by any other impediments. For, as the motions are equally changed, the changes of the velocities made toward contrary parts are reciprocally proportional to the bodies. This law takes place also in attractions, as will be proved in the next scholium.

In the above, as usual, motion is Newton's name for momentum, hence his careful distinction between motion and velocity.


The Third Law means that all forces are interactions - that there is no such thing as a unidirectional force. If body A exerts a force on body B, simultaneously, body B exerts the same force on body A. As shown in the diagram opposite, the skaters' forces on each other are equal in magnitude, and opposite in direction. Although the forces are equal, the accelerations are not: the less massive skater will have a greater acceleration due to Newton's second law. It is important to note that the action/reaction pair act on different objects and do not cancel each other out. The two forces in Newton's third law are of the same type, e.g., if the road exerts a forward frictional force on an accelerating car's tires, then it is also a frictional force that Newton's third law predicts for the tires pushing backward on the road.


Newton used the third law to derive the law of conservation of momentum;[20] however from a deeper perspective, conservation of momentum is the more fundamental idea (derived via Noether's theorem from Galilean invariance), and holds in cases where Newton's third law appears to fail, for instance when force fields as well as particles carry momentum, and in quantum mechanics. In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves. ... Noethers theorem is a central result in theoretical physics that shows that a conservation law can be derived from any continuous symmetry. ... Galilean invariance is a principle which states that the fundamental laws of physics are the same in all inertial (uniform-velocity) frames of reference. ... Originally a term coined by Michael Faraday to provide an intuitive paradigm, but theoretical construct (in the Kuhnian sense), for the behavior of electromagnetic fields, the term force field refers to the lines of force one object (the source object) exerts on another object or a collection of other objects. ... For a generally accessible and less technical introduction to the topic, see Introduction to quantum mechanics. ...


Importance and range of validity

Newton's laws were verified by experiment and observation for over 200 years, and they are excellent approximations at the scales and speeds of everyday life. Newton's laws of motion, together with his law of universal gravitation and the mathematical techniques of calculus, provided for the first time a unified quantitative explanation for a wide range of physical phenomena. This article covers the physics of gravitation. ... For other uses, see Calculus (disambiguation). ...


These three laws hold to a good approximation for macroscopic objects under everyday conditions. However, Newton's laws (combined with Universal Gravitation and Classical Electrodynamics) are inappropriate for use in certain circumstances, most notably at very small scales, very high speeds (in special relativity, the Lorentz factor must be included in the expression for momentum along with rest mass and velocity) or very strong gravitational fields. Therefore, the laws cannot be used to explain phenomena such as conduction of electricity in a semiconductor, optical properties of substances, errors in non-relativistically corrected GPS systems and superconductivity. Explanation of these phenomena requires more sophisticated physical theory, including General Relativity and Relativistic Quantum Mechanics. Classical electromagnetism is a theory of electromagnetism that was developed over the course of the 19th century, most prominently by James Clerk Maxwell. ... For a less technical and generally accessible introduction to the topic, see Introduction to special relativity. ... It has been suggested that Lorentz term be merged into this article or section. ... The term mass in special relativity is used in a couple of different ways, occasionally leading to a great deal of confusion. ... A semiconductor is a solid material that has electrical conductivity in between that of a conductor and that of an insulator; it can vary over that wide range either permanently or dynamically. ... Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ... A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. ... For a generally accessible and less technical introduction to the topic, see Introduction to general relativity. ... Quantum field theory (QFT) is the quantum theory of fields. ...


In quantum mechanics concepts such as force, momentum, and position are defined by linear operators that operate on the quantum state; at speeds that are much lower than the speed of light, Newton's laws are just as exact for these operators as they are for classical objects. At speeds comparable to the speed of light, the second law holds in the original form F=frac{mathrm{d}p}{mathrm{d}t}, which says that the force is the derivative of the momentum of the object with respect to time, but some of the newer versions of the second law (such as the constant mass approximation above) do not hold at relativistic velocities. For a generally accessible and less technical introduction to the topic, see Introduction to quantum mechanics. ... In mathematical formulations of quantum mechanics, an operator is a linear transformation from a Hilbert space to itself. ... Probability densities for the electron at different quantum numbers (l) In quantum mechanics, the quantum state of a system is a set of numbers that fully describe a quantum system. ...


Relationship to the conservation laws

In modern physics, the laws of conservation of momentum, energy, and angular momentum are of more general validity than Newton's laws, since they apply to both light and matter, and to both classical and non-classical physics. In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves. ... This article is about momentum in physics. ... This gyroscope remains upright while spinning due to its angular momentum. ...


This can be stated simply, "[Momentum, energy, angular momentum, matter] cannot be created or destroyed."


Because force is the time derivative of momentum, the concept of force is redundant and subordinate to the conservation of momentum, and is not used in fundamental theories (e.g. quantum mechanics, quantum electrodynamics, general relativity, etc.). The standard model explains in detail how the three fundamental forces known as gauge forces originate out of exchange by virtual particles. Other forces such as gravity and fermionic degeneracy pressure arise from conditions in the equations of motion in the underlying theories. For a generally accessible and less technical introduction to the topic, see Introduction to quantum mechanics. ... Quantum electrodynamics (QED) is a relativistic quantum field theory of electrodynamics. ... For a generally accessible and less technical introduction to the topic, see Introduction to general relativity. ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ... In physics, gauge theories are a class of physical theories based on the idea that symmetry transformations can be performed locally as well as globally. ... In the description of the interaction between elementary particles in quantum field theory, a virtual particle is a temporary elementary particle, used to describe an intermediate stage in the interaction. ... Gravity redirects here. ... The Pauli exclusion principle is a quantum mechanical principle formulated by Wolfgang Pauli in 1925. ...


Newton stated the third law within a world-view that assumed instantaneous action at a distance between material particles. However, he was prepared for philosophical criticism of this action at a distance, and it was in this context that he stated the famous phrase "I feign no hypotheses". In modern physics, action at a distance has been completely eliminated, except for subtle effects involving quantum entanglement. In physics, action at a distance is the interaction of two objects which are separated in space with no known mediator of the interaction. ... Hypotheses non fingo is a Latin phrase attributed to Isaac Newton often translated as, I make no hypotheses. The context is that he is refusing to speculate as the the whys of the laws of nature, confining himself entirely to their phenomenal description. ... It has been suggested that Quantum coherence be merged into this article or section. ...


Conservation of energy was discovered nearly two centuries after Newton's lifetime, the long delay occurring because of the difficulty in understanding the role of microscopic and invisible forms of energy such as heat and infra-red light.


References and notes

  1. ^ The Second Law asserts "The time-rate-of-change of a quantity called momentum is proportional to the force." RP Feynman, Leighton RB & Sands M (2005). The Feynman Lectures on Physics. San Francisco: Pearson/Addison-Wesley, Vol. 1, p. 9-1. ISBN 0805390499. 
  2. ^ C. E. Linebarger, Silas Ellsworth Coleman (1911). A Text-book of Physics. Boston MA: DC Heath, p. 128. 
  3. ^ Denny K. Miu (1992). Mechatronics: Electromechanics and Contromechanics. Berlin: Springer, p. 9. ISBN 0387978933. 
  4. ^ Neville G. Warren (2000). Excel Preliminary Physics. Glebe NSW: Pascal Press, p.121. ISBN 1740200853. 
  5. ^ Ahmed A. Shabana (2005). Dynamics of Multibody Systems, Third Edition, Cambridge UK: Cambridge University Press, p.174. ISBN 0511115830. 
  6. ^ Isaac Newton, The Principia, A new translation by I.B. Cohen and A. Whitman, University of California press, Berkeley 1999.
  7. ^ Galili, I. & Tseitlin, M. (2003), "Newton's first law: text, translations, interpretations, and physics education.", Science and Education 12 (1): 45-73 
  8. ^ a b NMJ Woodhouse (2003). Special relativity. London/Berlin: Springer, p. 6. ISBN 1-85233-426-6. 
  9. ^ On a more technical note, although Newton's laws are not applicable on non-inertial frames of reference, such as the accelerating airplane, they can be made to do so with the introduction of a "fictitious force" acting on the entire system: basically, by introducing a force that quantifies the anomalous motion of objects within that system (such as the ball moving without an apparent influence in the example above).
  10. ^ Abdus Salam (1984), "Islam and Science". In C. H. Lai (1987), Ideals and Realities: Selected Essays of Abdus Salam, 2nd ed., World Scientific, Singapore, p. 179-213.
  11. ^ Fernando Espinoza (2005). "An analysis of the historical development of ideas about motion and its implications for teaching", Physics Education 40 (2), p. 141.
  12. ^ According to Maxwell in Matter and Motion, Newton meant by motion "the quantity of matter moved as well as the rate at which it travels" and by impressed force he meant "the time during which the force acts as well as the intensity of the force". See Harman and Shapiro, cited below.
  13. ^ The use of algebraic expressions became popular during the 18th century, after Newton's death, while vector notation dates to the late 19th century. The Principia expresses mathematical theorems in words and consistently uses geometrical rather than algebraic proofs.
  14. ^ I Bernard Cohen (Peter M. Harman & Alan E. Shapiro, Eds) (2002). The investigation of difficult things : essays on Newton and the history of the exact sciences in honour of D.T. Whiteside. Cambridge UK: Cambridge University Press, p. 353. ISBN 052189266X. 
  15. ^ Hannah, J, Hillier, M J, Applied Mechanics, p221, Pitman Paperbacks, 1971
  16. ^ Raymond A. Serway, Jerry S. Faughn (2006). College Physics. Pacific Grove CA: Thompson-Brooks/Cole, p. 161. ISBN 0534997244. 
  17. ^ WJ Stronge (2004). Impact mechanics. Cambridge UK: Cambridge University Press, pp. 12 ff. ISBN 0521602890. 
  18. ^ C Møller (1976). The Theory of Relativity, Second Edition, Oxford UK: Oxford University Press, pp. 70-75. ISBN 019560539X. 
  19. ^ The following quote is an exact reproduction from Physics part I by Halliday and Resnick, page 199:
    "It is important to note that we cannot derive a general expression for Newton's second law for variable mass systems by treating the mass in F = dP/dt = d(Mv) as a variable." (All emphasis in original)
    A few lines later, they again say:
    "We can use F = dP/dt to analyze variable mass systems only if we apply it to an entire system of constant mass having parts among which there is an interchange of mass."
    Kleppner and Kolenkow say the following in page 133-134:
    "Recall that F = dP/dt was established for a system composed of a certain set of particles...it is essential to deal with the same set of particles throughout the time interval...Consequently, the mass of the system can not change during the time of interest."
  20. ^ Newton, Principia, Corollary III to the laws of motion

A fictitious force is an apparent force that acts on all masses in a non-inertial frame of reference, e. ... For other uses, see Abdus Salam (disambiguation). ...

Further reading

  • Marion, Jerry and Thornton, Stephen. Classical Dynamics of Particles and Systems. Harcourt College Publishers, 1995. ISBN 0-03-097302-3
  • Fowles, G. R. and Cassiday, G. L. Analytical Mechanics (6ed). Saunders College Publishing, 1999. ISBN 0-03-022317-2
  • Feynman R P, Leighton R B & Sands M (2006). The Feynman lectures on physics Vol. 1. Pearson/Addison-Wesley. ISBN 0805390499. 

See also

This is a list of scientific laws named after people (eponymous laws). ... This article is about the planet. ... Galilean invariance is a principle which states that the fundamental laws of physics are the same in all inertial (uniform-velocity) frames of reference. ... In physics, Modified Newtonian dynamics (MOND) is a theory that proposes a modification of Newtons Second Law of Dynamics, to explain the galaxy rotation problem. ... Lagrangian mechanics is a re-formulation of classical mechanics that combines conservation of momentum with conservation of energy. ... The principle of least action was first formulated by Pierre-Louis Moreau de Maupertuis, who said that Nature is thrifty in all its actions. See action (physics). ...

External links


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