Talk:Motion

message: There were a few flaws in the introduction section. 
* "motion is the result of applied force" is 99% correct, but it could be misunderstood as that sustained motion required sustained applied force (as was wrongly believed in ancient times). Basically, applied force results in change in motion. Linear motion is the result of absent (resulting) force). 
* "Constant motion is the natural state of anything in the universe"‽ Give me a break! That's something you can tell your kids when they are 3. But it's just too wrong for an encyclopedia. Please don't believe everything that some kind of professor said...  There is no notion of a "natural state" in physics. And most motion is definitely not constant! 
* Laws in physics (or in any other science) are not responsible for anything, they do not cause anything. They are describe the nature. (Think about that!)
Tang Wenlong (talk) 20:34, 18 March 2008 (UTC)
replies: text:  Nice job in improving clarity and brevity of the intro. Earthdirt (talk) 02:42, 19 March 2008 (UTC)
thread_title:  Intro - Motion, momentum, etc. 

message: all kinds of motion are-
1.rotatory motion,
2.rectilinear motion,
3.translatory motion,
4.curvelinear motion,
5.oscilatory motion,
6.vibratory motion,
7.periodic motion,
8.non-periodic motion,
9.unoform motion,
10.non-uniform motion.
=== According to rate ===
1) uniform motion
2) (uniformly) accelerated motion
3) (uniformly) deceleretated
--Ionn-Korr 21:30, 27 October 2005 (UTC)
thread_title:  Kinds of motion 

message: 1) uniform motion
2) (uniformly) accelerated motion
3) (uniformly) deceleretated
--Ionn-Korr 21:30, 27 October 2005 (UTC)
thread_title:  According to rate 

message: I think we have the definition of motion wrong. If you put time into the definition, doesn't that become a measurement of speed? Hmmm?
Ye mi too (am JAZ 4rm Nig)no at all.
:I could argue otherwise. If time equals speed, then speed wouldn't neccessarily exist. You see, all of time, every impossibly small fraction of a second, contains an impossibly large amount of moments. To measure speed, you would need some kind of motion, even 0.0(repeating)1x10-99999(repeating) fm. However, an instant, a nothingth of a second, can have no movement. Therefore, even if multiplied infinitely, the 0 speed of an object in an instant would be 0. Now some would argue that 0 time has 0 speed, and x time would have y speed, so it isn't of any effect. However, if this moment in question doesn't matter, neither would any other. What would happen if you didn't have a single instant ever? There would be no time. There just isn't motion in a moment, so that means that if you don't have any of something in an increment, it wouldn't be in any larger incriments. By using time=speed, I could argue that motion is an illusion and all motion is stroboscopic. ChristopherEdwards 17:49, 5 October 2007 (UTC)
thread_title:  Motion defined by time = speed, yes? 

message: There are four main types of motion.There's rotational, linear, reciprocating and also  oscillating. —The preceding unsigned comment was added by 74.117.131.130 (talk) 22:15, 25 February 2007 (UTC)
thread_title:  motion 

message: This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 04:18, 10 November 2007 (UTC)
thread_title:  WikiProject class rating

message: i do not understand any of this info!!!!YOLO!!!  —Preceding unsigned comment added by 71.194.212.28 (talk) 11:23, 9 May 2009 (UTC)
thread_title:  huh? 

message: Those aren't Newton's Laws of Motion. Those are a modern rephrasing of Newton's Laws of Motion (and not all that accurate, defining force to be mass times acceleration!). Also, as far as defining motion is concerned, if this article has anything to do with Newton, you should look to how Newton defines "quantity of motion." It isn't merely an object's change in position with respect to time, which would be speed. 
Further, the article needs a history section. There was a long line of thoughts about motion before Newton, going back to the ancient Greeks: pre-Socratics, Plato, Aristotle. JKeck (talk) 19:35, 25 April 2011 (UTC)
thread_title:  Newton and Motion 

message: The brief section on kinematics seems to state only that there are two types of motion uniform and non-uniform.  This seems obvious and not very helpful.  I think revisions are needed.  Prof McCarthy (talk) 06:40, 2 January 2012 (UTC)
replies: text: I replaced this section with a discussion of planar, spherical and spatial motion of machine systems.Prof McCarthy (talk) 12:10, 2 January 2012 (UTC)
thread_title:  Section on kinematics 

message: The lead to this article talks about "change in action," momentum and forces more than it introduces motion. Prof McCarthy (talk) 12:32, 2 January 2012 (UTC)
thread_title:  Edits to the lead 

message: I am not sure that motion is best understood to mean: "More generally, the term motion signifies any temporal change in a physical system."  An increase in temperature, elongation under load, or a chemical change could correctly be viewed as motion at an atomic level, but "motion" is not the first thing that comes to mind in these physical processes. So this seems an awkward way of describing motion.  In addition, I realize there is a desire to include motions of quantum particles, but I do not believe it is correct to say that "the concept of position does not apply."  The specific position that a sub-atomic particle can occupy with a prescribed probability is well-defined in quantum mechanics. Prof McCarthy (talk) 06:15, 10 January 2012 (UTC)
thread_title:  Temporal change 

message: motion is the changing in distance of an object to a reference point. you other people made that concept way to complicated.  — Preceding unsigned comment added by 68.50.153.61 (talk) 17:35, 4 May 2013 (UTC)
thread_title:  Motion 

message: The Light section in this article seems irrelevant. I really don't get how light came into this subject on motion.
Motion is not the change in position of an object with reference to time, but just with its initial reference point.... 
Motion is just the change in position of an object...
A_Random_Person (talk) 18:53, 7 June 2013 (UTC)
thread_title:  Light??? And the definition of motion seems to be wrong... 

message: The article does not mention degrees of freedom (physics). It is not good, because the motion degrees of freedom pertain to any particle and have the same description (save for peculiarities of massless particles), whereas internal degrees of freedom do not have a uniform description, both classical and quantum. Also, the article should explicitly name and distinguish translational motion and its standard descriptions (velocity and wave function respectively), and rotational motion and its descriptions (angular velocity and angular momentum operator respectively). Incnis Mrsi (talk) 08:51, 17 January 2014 (UTC)
thread_title:  Degrees of freedom 

message: 1: A is steady, when
  2: B acts on A, then
  3: A reacts to B, end. 
--KYPark (talk) 16:39, 24 January 2016 (UTC)
thread_title:  Newton's laws in motion  

message: Lorentz force f on a charged particle (of charge q) in motion (instantaneous velocity v). The Efield and B field vary in space and time.
In electrodynamics, the force on a charged particle of charge q is the Lorentz force:[21]
:
Combining with Newton's second law gives a first order differential equation of motion, in terms of position of the particle:
:
or its momentum:
:
The same equation can be obtained using the Lagrangian (and applying Lagrange's equations above) for a charged particle of mass m and charge q:[22]
:
where A and ϕ are the electromagnetic scalar and vector potential fields. The Lagrangian indicates an additional detail: the canonical momentum in Lagrangian mechanics is given by:
:
instead of just mv, implying the motion of a charged particle is fundamentally determined by the mass and charge of the particle. The Lagrangian expression was first used to derive the force equation.
Alternatively the Hamiltonian (and substituting into the equations):[20]
:
can derive the Lorentz force equation.
=== General relativity[edit source | edit] ===
==== Geodesic equation of motion[edit source | edit] ====
Geodesics on a sphere are arcs of great circles (yellow curve). On a2D–manifold (such as the sphere shown), the direction of the accelerating geodesic is uniquely fixed if the separation vector ξ isorthogonal to the "fiducial geodesic" (green curve). As the separation vector ξ0 changes to ξ after a distance s, the geodesics are not parallel (geodesic deviation).[23]
Main articles: Geodesics in general relativity and Geodesic equation
The above equations are valid in flat spacetime. In curved space spacetime, things become mathematically more complicated since there is no straight line; this is generalized and replaced by a geodesic of the curved spacetime (the shortest length of curve between two points). For curved manifolds with a metric tensor g, the metric provides the notion of arc length (see line element for details), the differential arc length is given by:[24]
:
and the geodesic equation is a second-order differential equation in the coordinates, the general solution is a family of geodesics:[25]
:
where Γ μαβ is a Christoffel symbol of the second kind, which contains the metric (with respect to the coordinate system).
Given the mass-energy distribution provided by the stress–energy tensor T αβ, the Einstein field equations are a set of non-linear second-order partial differential equations in the metric, and imply the curvature of space time is equivalent to a gravitational field (see principle of equivalence). Mass falling in curved spacetime is equivalent to a mass falling in a gravitational field - because gravity is a fictitious force. The relative acceleration of one geodesic to another in curved spacetime is given by the geodesic deviation equation:
:
where ξα = x2α − x1α is the separation vector between two geodesics, D/ds (not just d/ds) is the covariant derivative, and Rαβγδ is the Riemann curvature tensor, containing the Christoffel symbols. In other words, the geodesic deviation equation is the equation of motion for masses in curved spacetime, analogous to the Lorentz force equation for charges in an electromagnetic field.[26]
For flat spacetime, the metric is a constant tensor so the Christoffel symbols vanish, and the geodesic equation has the solutions of straight lines. This is also the limiting case when masses move according to Newton's law of gravity.
==== Spinning objects[edit source | edit] ====
In general relativity, rotational motion is described by the relativistic angular momentum tensor, including the spin tensor, which enter the equations of motion under covariant derivatives with respect to proper time. The Mathisson–Papapetrou–Dixon equations describe the motion of spinning objects moving in a gravitational field.
=== Analogues for waves and fields[edit source | edit] ===
Unlike the equations of motion for describing particle mechanics, which are systems of coupled ordinary differential equations, the analogous equations governing the dynamics of waves andfields are always partial differential equations, since the waves or fields are functions of space and time. For a particular solution, boundary conditions along with initial conditions need to be specified.
Sometimes in the following contexts, the wave or field equations are also called "equations of motion".
==== Field equations[edit source | edit] ====
Equations that describe the spatial dependence and time evolution of fields are called field equations. These include
* Maxwell's equations for the electromagnetic field,
* Poisson's equation for Newtonian gravitational or electrostatic field potentials,
* the Einstein field equation for gravitation (Newton's law of gravity is a special case for weak gravitational fields and low velocities of particles).
This terminology is not universal: for example although the Navier–Stokes equations govern the velocity field of a fluid, they are not usually called "field equations", since in this context they represent the momentum of the fluid and are called the "momentum equations" instead.
==== Wave equations[edit source | edit] ====
Equations of wave motion are called wave equations. The solutions to a wave equation give the time-evolution and spatial dependence of the amplitude. Boundary conditions determine if the solutions describe traveling waves or standing waves.
From classical equations of motion and field equations; mechanical, gravitational wave, and electromagnetic wave equations can be derived. The general linear wave equation in 3D is:
:
where X = X(r, t) is any mechanical or electromagnetic field amplitude, say:[27]
* the transverse or longitudinal displacement of a vibrating rod, wire, cable, membrane etc.,
* the fluctuating pressure of a medium, sound pressure,
* the electric fields E or D, or the magnetic fields B or H,
* the voltage V or current I in an alternating current circuit,
and v is the phase velocity. Nonlinear equations model the dependence of phase velocity on amplitude, replacing v by v(X). There are other linear and nonlinear wave equations for very specific applications, see for example the Korteweg–de Vries equation.
==== Quantum theory[edit source | edit] ====
In quantum theory, the wave and field concepts both appear.
In quantum mechanics, in which particles also have wave-like properties according to wave–particle duality, the analogue of the classical equations of motion (Newton's law, Euler–Lagrange equation, Hamilton–Jacobi equation, etc.) is the Schrödinger equation in its most general form:
:
where Ψ is the wavefunction of the system, Ĥ is the quantum Hamiltonian operator, rather than a function as in classical mechanics, and ħ is the Planck constant divided by 2π. Setting up the Hamiltonian and inserting it into the equation results in a wave equation, the solution is the wavefunction as a function of space and time. The Schrödinger equation itself reduces to the Hamilton–Jacobi equation in when one considers the correspondence principle, in the limit that ħ becomes zero.
Throughout all aspects of quantum theory, relativistic or non-relativistic, there are various formulations alternative to the Schrödinger equation that govern the time evolution and behavior of a quantum system, for instance:
* the Heisenberg equation of motion resembles the time evolution of classical observables as functions of position, momentum, and time, if one replaces dynamical observables by theirquantum operators and the classical Poisson bracket by the commutator,
* the phase space formulation closely follows classical Hamiltonian mechanics, placing position and momentum on equal footing,
* the Feynman path integral formulation extends the principle of least action
The material above was added 13 March 2016 at 14:25 (UTC) by User:Varshit1234. Some of it may be useful in the article. Just plain Bill (talk) 15:21, 13 March 2016 (UTC)
thread_title:  Electrodynamics[edit source | edit] 

message: Unlike the equations of motion for describing particle mechanics, which are systems of coupled ordinary differential equations, the analogous equations governing the dynamics of waves andfields are always partial differential equations, since the waves or fields are functions of space and time. For a particular solution, boundary conditions along with initial conditions need to be specified.
Sometimes in the following contexts, the wave or field equations are also called "equations of motion".
==== Field equations[edit source | edit] ====
Equations that describe the spatial dependence and time evolution of fields are called field equations. These include
* Maxwell's equations for the electromagnetic field,
* Poisson's equation for Newtonian gravitational or electrostatic field potentials,
* the Einstein field equation for gravitation (Newton's law of gravity is a special case for weak gravitational fields and low velocities of particles).
This terminology is not universal: for example although the Navier–Stokes equations govern the velocity field of a fluid, they are not usually called "field equations", since in this context they represent the momentum of the fluid and are called the "momentum equations" instead.
==== Wave equations[edit source | edit] ====
Equations of wave motion are called wave equations. The solutions to a wave equation give the time-evolution and spatial dependence of the amplitude. Boundary conditions determine if the solutions describe traveling waves or standing waves.
From classical equations of motion and field equations; mechanical, gravitational wave, and electromagnetic wave equations can be derived. The general linear wave equation in 3D is:
:
where X = X(r, t) is any mechanical or electromagnetic field amplitude, say:[27]
* the transverse or longitudinal displacement of a vibrating rod, wire, cable, membrane etc.,
* the fluctuating pressure of a medium, sound pressure,
* the electric fields E or D, or the magnetic fields B or H,
* the voltage V or current I in an alternating current circuit,
and v is the phase velocity. Nonlinear equations model the dependence of phase velocity on amplitude, replacing v by v(X). There are other linear and nonlinear wave equations for very specific applications, see for example the Korteweg–de Vries equation.
==== Quantum theory[edit source | edit] ====
In quantum theory, the wave and field concepts both appear.
In quantum mechanics, in which particles also have wave-like properties according to wave–particle duality, the analogue of the classical equations of motion (Newton's law, Euler–Lagrange equation, Hamilton–Jacobi equation, etc.) is the Schrödinger equation in its most general form:
:
where Ψ is the wavefunction of the system, Ĥ is the quantum Hamiltonian operator, rather than a function as in classical mechanics, and ħ is the Planck constant divided by 2π. Setting up the Hamiltonian and inserting it into the equation results in a wave equation, the solution is the wavefunction as a function of space and time. The Schrödinger equation itself reduces to the Hamilton–Jacobi equation in when one considers the correspondence principle, in the limit that ħ becomes zero.
Throughout all aspects of quantum theory, relativistic or non-relativistic, there are various formulations alternative to the Schrödinger equation that govern the time evolution and behavior of a quantum system, for instance:
* the Heisenberg equation of motion resembles the time evolution of classical observables as functions of position, momentum, and time, if one replaces dynamical observables by theirquantum operators and the classical Poisson bracket by the commutator,
* the phase space formulation closely follows classical Hamiltonian mechanics, placing position and momentum on equal footing,
* the Feynman path integral formulation extends the principle of least action
The material above was added 13 March 2016 at 14:25 (UTC) by User:Varshit1234. Some of it may be useful in the article. Just plain Bill (talk) 15:21, 13 March 2016 (UTC)
thread_title:  Analogues for waves and fields[edit source | edit] 

message: In quantum theory, the wave and field concepts both appear.
In quantum mechanics, in which particles also have wave-like properties according to wave–particle duality, the analogue of the classical equations of motion (Newton's law, Euler–Lagrange equation, Hamilton–Jacobi equation, etc.) is the Schrödinger equation in its most general form:
:
where Ψ is the wavefunction of the system, Ĥ is the quantum Hamiltonian operator, rather than a function as in classical mechanics, and ħ is the Planck constant divided by 2π. Setting up the Hamiltonian and inserting it into the equation results in a wave equation, the solution is the wavefunction as a function of space and time. The Schrödinger equation itself reduces to the Hamilton–Jacobi equation in when one considers the correspondence principle, in the limit that ħ becomes zero.
Throughout all aspects of quantum theory, relativistic or non-relativistic, there are various formulations alternative to the Schrödinger equation that govern the time evolution and behavior of a quantum system, for instance:
* the Heisenberg equation of motion resembles the time evolution of classical observables as functions of position, momentum, and time, if one replaces dynamical observables by theirquantum operators and the classical Poisson bracket by the commutator,
* the phase space formulation closely follows classical Hamiltonian mechanics, placing position and momentum on equal footing,
* the Feynman path integral formulation extends the principle of least action
The material above was added 13 March 2016 at 14:25 (UTC) by User:Varshit1234. Some of it may be useful in the article. Just plain Bill (talk) 15:21, 13 March 2016 (UTC)
thread_title:  Quantum theory[edit source | edit] 

message: As I understand it , a position vector only includes information about location w.r.t. a reference point, without specifying the attitude or orientation of the object. A quick reading of the lead paragraph offers no hint that rotation may also be described as motion. (There are other issues with clarity and quality of sourcing, but this may be enough to open discussion with...) Just plain Bill (talk) 14:29, 15 November 2016 (UTC)
thread_title:  Definition in lead seems to exclude rotation 

message: IT IS A BELIEF OF SOME SCIENTISTS LIKE EINSTIEN THAT THERE EXISTS A OTHER WORLD AND THIS WORLD IS ITS COPY . IT IS GIVEN AS PER THE THEORY OF "MANY WORLDS" BY EINSTEIN Aabina shah (talk) 07:21, 15 December 2017 (UTC)
thread_title:  WHAT IS A MIRROR WORLD ? 

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thread_title:  External links modified (January 2018) 

message: I think you should give a little more about the motion because it will help us to understand it briefly  Sarajit roy 678 (talk) 04:10, 6 October 2018 (UTC)
thread_title:  Motion 

message: The entire section titled "Classical Mechanics" is just a different (and slightly expanded) version of the preceding text. Be it the significance of classical mechanics to the laws of motion to what classical mechanics describes; it's the same thing.
Emdosis (talk) 01:13, 10 October 2021 (UTC)
thread_title:  Classical Mechanics 

message: — Assignment last updated by Janyahmercedes (talk) 02:52, 26 January 2023 (UTC)
thread_title: Wiki Education assignment: PHY 381 History of Modern Physics

message: I'm undoing Special:Diff/1131381527 "(Sorted bullet lists using ListSorter)" since it broke the formatting. It moved most, but not all, of a long reference from the text into the "See also" section, leaving the  behind, and moved bulleted items from the "Types of motion" section up to where the reference used to be. This looks odd and was certainly not a minor edit. I believe the following two edits were only trying to fix up the problems caused by the first edit, so I'm going to restore the version before the first edit. -- John of Reading (talk) 11:09, 12 January 2023 (UTC)
thread_title:  ListSorter