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In "physics, motion is a change in "position of an object over time. Motion is described in terms of "displacement, "distance, "velocity, "acceleration, "time and "speed. Motion of a body is observed by attaching a "frame of reference to an observer and measuring the change in position of the body relative to that frame.

If the position of a body is not changing with respect to a given frame of reference, the body is said to be at rest, motionless, immobile, stationary, or to have constant ("time-invariant) position. An object's motion cannot change unless it is acted upon by a "force, as described. Momentum is a quantity which is used for measuring the motion of an object. An object's "momentum is directly related to the object's "mass and velocity, and the total momentum of all objects in an isolated system (one not affected by external forces) does not change with time, as described by the "law of conservation of momentum.

As there is no absolute frame of reference, "absolute motion cannot be determined.[1] Thus, everything in the universe can be considered to be moving.[2]:20–21

Motion applies to objects, bodies, and matter particles, to radiation, radiation fields and radiation particles, and to space, its curvature and space-time. One can also speak of motion of shapes and boundaries. So, the term motion, in general, signifies a continuous change in the configuration of a physical system. For example, one can talk about motion of a wave or about motion of a quantum particle, where the configuration consists of probabilities of occupying specific positions.

Motion involves a change in position, such as in this perspective of rapidly leaving "Yongsan Station.


Laws of motion[edit]

In physics, motion is described through two sets of apparently contradictory "laws of mechanics. Motions of all large-scale and familiar objects in the universe (such as "projectiles, "planets, "cells, and "humans) are described by "classical mechanics. Whereas the motion of very small "atomic and "sub-atomic objects is described by "quantum mechanics.

First law: In an "inertial reference frame, an object either remains at rest or continues to move at a constant "velocity, unless acted upon by a "net force.
Second law: In an inertial reference frame, the vector "sum of the "forces F on an object is equal to the "mass m of that object multiplied by the "acceleration a of the object: F = ma.
Third law: When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.

Classical mechanics[edit]

Classical mechanics 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. It produces very accurate results within these domains, and is one of the oldest and largest in "science, "engineering, and "technology.

Classical mechanics is fundamentally based on "Newton's laws of motion. These laws describe the relationship between the forces acting on a body and the motion of that body. They were first compiled by "Sir Isaac Newton in his work "Philosophiæ Naturalis Principia Mathematica, first published on July 5, 1687. Newton"s three laws are:

  1. A "body either is at rest or moves with constant velocity, until and unless an outer force is applied to it.
  2. An object will travel in one direction only until an outer force changes its direction.
  3. Whenever one body exerts a force F onto a second body,(in some cases, which is standing still) the second body exerts the force −F on the first body. F and −F are equal in magnitude and opposite in sense. So, the body which exerts F will go backwards.[3]

Newton's three laws of motion were the first to accurately provide a mathematical model for understanding "orbiting bodies in "outer space. This explanation unified the motion of celestial bodies and motion of objects on earth.

Classical mechanics was later further enhanced by "Albert Einstein's "special relativity and "general relativity. Special relativity is concerned with the motion of objects with a high "velocity, approaching the "speed of light; general relativity is employed to handle "gravitational motion at a deeper level.

Uniform Motion:

When an object moves with a constant speed at a particular direction at regular intervals of time it's known as the uniform motion. For example: a bike moving in a straight line with a constant speed.


If v = final velocity, u = initial velocity, a = acceleration, t = time, s = displacement, then :

v = u + at, v = at

s = ut + 1/2at2, s = 1/2at2

v2 = u2 + 2as, v2 = 2as

Quantum mechanics[edit]

"Quantum mechanics is a set of principles describing "physical reality at the atomic level of matter ("molecules and "atoms) and the "subatomic particles ("electrons, "protons, "neutrons, and even smaller "elementary particles such as "quarks). These descriptions include the simultaneous wave-like and particle-like behavior of both "matter and "radiation energy as described in the "wave–particle duality.["citation needed]

In classical mechanics, accurate "measurements and "predictions of the state of objects can be calculated, such as "location and "velocity. In the quantum mechanics, due to the "Heisenberg uncertainty principle, the complete state of a subatomic particle, such as its location and velocity, cannot be simultaneously determined.["citation needed]

In addition to describing the motion of atomic level phenomena, quantum mechanics is useful in understanding some large-scale phenomenon such as "superfluidity, "superconductivity, and "biological systems, including the function of "smell receptors and the "structures of proteins.["citation needed]

List of "imperceptible" human motions[edit]

Humans, like all known things in the universe, are in constant motion,[2]:8–9 however, aside from obvious movements of the various external "body parts and "locomotion, humans are in motion in a variety of ways which are more difficult to "perceive. Many of these "imperceptible motions" are only perceivable with the help of special tools and careful observation. The larger scales of "imperceptible motions" are difficult for humans to perceive for two reasons: 1) "Newton's laws of motion (particularly "Inertia) which prevent humans from feeling motions of a mass to which they are connected, and 2) the lack of an obvious "frame of reference which would allow individuals to easily see that they are moving.[4] The smaller scales of these motions are too small for "humans to "sense.



Sun and solar system[edit]



Internal body[edit]


The "cells of the "human body have many structures which move throughout them.


Subatomic particles[edit]


Light propagates at 299,792,458 m/s, often approximated as 299,792 kilometres per second or 186,282 miles per second. The speed of light (or c) is also the speed of all "massless particles and associated "fields in a vacuum, and it is the upper limit on the speed at which energy, matter, and "information can travel. The speed of light is the limit of speed for physical systems.

In addition, the speed of light is an invariant quantity: it has the same value, irrespective of the position or speed of the observer. This property makes the speed of light c the natural measurement unit for speed.

Types of motion[edit]

Fundamental motions[edit]

See also[edit]


  1. ^ Wahlin, Lars (1997). "9.1 Relative and absolute motion". The Deadbeat Universe (PDF). Boulder, CO: Coultron Research. pp. 121–129. "ISBN "0-933407-03-3. Retrieved 25 January 2013. 
  2. ^ a b Tyson, Neil de Grasse; Charles Tsun-Chu Liu; Robert Irion (2000). The universe : at home in the cosmos. Washington, DC: "National Academy Press. "ISBN "0-309-06488-0. 
  3. ^ Newton's "Axioms or Laws of Motion" can be found in the ""Principia" on page 19 of volume 1 of the 1729 translation.
  4. ^ Safkan, Yasar. "Question: If the term 'absolute motion' has no meaning, then why do we say that the earth moves around the sun and not vice versa?". Ask the Experts. Retrieved 25 January 2014. 
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  6. ^ Kogut, A.; Lineweaver, C.; Smoot, G. F.; Bennett, C. L.; Banday, A.; Boggess, N. W.; Cheng, E. S.; de Amici, G.; Fixsen, D. J.; Hinshaw, G.; Jackson, P. D.; Janssen, M.; Keegstra, P.; Loewenstein, K.; Lubin, P.; Mather, J. C.; Tenorio, L.; Weiss, R.; Wilkinson, D. T.; Wright, E. L. (1993). "Dipole Anisotropy in the COBE Differential Microwave Radiometers First-Year Sky Maps". Astrophysical Journal. 419: 1. "arXiv:astro-ph/9312056Freely accessible. "Bibcode:1993ApJ...419....1K. "doi:10.1086/173453. 
  7. ^ Imamura, Jim (August 10, 2006). "Mass of the Milky Way Galaxy". "University of Oregon. Archived from the original on 2007-03-01. Retrieved 2007-05-10. 
  8. ^ Ask an Astrophysicist. NASA Goodard Space Flight Center.
  9. ^ Williams, David R. (September 1, 2004). "Earth Fact Sheet". "NASA. Retrieved 2007-03-17. 
  10. ^ Staff. "GPS Time Series". "NASA JPL. Retrieved 2007-04-02. 
  11. ^ Huang, Zhen Shao (2001). Glenn Elert, ed. "Speed of the Continental Plates". The Physics Facebook. Retrieved 2016-12-29. 
  12. ^ Meschede, M.; Udo Barckhausen, U. (November 20, 2000). "Plate Tectonic Evolution of the Cocos-Nazca Spreading Center". Proceedings of the Ocean Drilling Program. "Texas A&M University. Retrieved 2007-04-02. 
  13. ^ Wexler, L.; D H Bergel; I T Gabe; G S Makin; C J Mills (1 September 1968). "Velocity of Blood Flow in Normal Human Venae Cavae". Circulation Research. 23 (3): 349–359. "doi:10.1161/01.RES.23.3.349. 
  14. ^ Bowen, R (27 May 2006). "Gastrointestinal Transit: How Long Does It Take?". Pathophysiology of the digestive system. "Colorado State University. Retrieved 25 January 2014. 
  15. ^ M. Fischer; U. K. Franzeck; I. Herrig; U. Costanzo; S. Wen; M. Schiesser; U. Hoffmann; A. Bollinger (1 January 1996). "Flow velocity of single lymphatic capillaries in human skin". Am J Physiol Heart Circ Physiol. 270 (1): H358–H363. "PMID 8769772. Retrieved 2007-11-14. 
  16. ^ "cytoplasmic streaming - biology". Encyclopædia Britannica. 
  17. ^ "Microtubule Motors". 
  18. ^ Hill, David; Holzwarth, George; Bonin, Keith (2002). "Velocity and Drag Forces on motor-protein-driven Vesicles in Cells". American Physical Society, the 69th Annual Meeting of the Southeastern. abstract. #EA.002. "Bibcode:2002APS..SES.EA002H. 
  19. ^ Temperature and BEC. Physics 2000: Colorado State University Physics Department
  20. ^ "Classroom Resources - Argonne National Laboratory". 
  21. ^ Chapter 2, Nuclear Science- A guide to the nuclear science wall chart. Berkley National Laboratory.
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