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| ==Origin== | | ==Origin== |
| [https://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English], from [[Latin]] collision-, collisio, from collidere | | [https://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English], from [[Latin]] collision-, collisio, from collidere |
− | *[http://en.wikipedia.org/wiki/15th_century 15th Century] | + | *[https://en.wikipedia.org/wiki/15th_century 15th Century] |
| ==Definitions== | | ==Definitions== |
| *1: an [[act]] or instance of colliding : clash | | *1: an [[act]] or instance of colliding : clash |
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| The [[magnitude]] of the [[velocity]] [[difference]] at impact is called the closing speed. | | The [[magnitude]] of the [[velocity]] [[difference]] at impact is called the closing speed. |
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− | The field of [http://en.wikipedia.org/wiki/Dynamics_(mechanics) dynamics] is concerned with moving and colliding objects. | + | The field of [https://en.wikipedia.org/wiki/Dynamics_(mechanics) dynamics] is concerned with moving and colliding objects. |
| ==Elastic and Inelastic Collisions== | | ==Elastic and Inelastic Collisions== |
− | A perfectly [http://en.wikipedia.org/wiki/Elastic_collision elastic collision] is defined as one in which there is no loss of [http://en.wikipedia.org/wiki/Kinetic_energy kinetic energy] in the collision. An inelastic collision is one in which part of the kinetic energy is changed to some other [[form]] of [[energy]] in the collision. Any macroscopic collision between objects will [[convert]] some of the kinetic energy into [http://en.wikipedia.org/wiki/Internal_energy internal energy] and other forms of energy, so no large scale impacts are perfectly elastic. [[Momentum]] is conserved in inelastic collisions, but one cannot track the kinetic energy through the collision since some of it is converted to other forms of energy. Collisions in [http://en.wikipedia.org/wiki/Ideal_gases ideal gases] approach perfectly elastic collisions, as do scattering [[interactions]] of [http://en.wikipedia.org/wiki/Sub-atomic_particles sub-atomic particles] which are deflected by the [[electromagnetic]] force. Some large-scale interactions like the slingshot type [[gravitation]]al interactions between [[satellites]] and [[planets]] are perfectly elastic. Collisions between hard [[spheres]] may be nearly elastic, so it is useful to [[calculate]] the limiting case of an elastic collision. The [[assumption]] of [[conservation]] of [[momentum]] as well as the conservation of kinetic energy makes possible the [[calculation]] of the final velocities in two-body collisions. | + | A perfectly [https://en.wikipedia.org/wiki/Elastic_collision elastic collision] is defined as one in which there is no loss of [https://en.wikipedia.org/wiki/Kinetic_energy kinetic energy] in the collision. An inelastic collision is one in which part of the kinetic energy is changed to some other [[form]] of [[energy]] in the collision. Any macroscopic collision between objects will [[convert]] some of the kinetic energy into [https://en.wikipedia.org/wiki/Internal_energy internal energy] and other forms of energy, so no large scale impacts are perfectly elastic. [[Momentum]] is conserved in inelastic collisions, but one cannot track the kinetic energy through the collision since some of it is converted to other forms of energy. Collisions in [https://en.wikipedia.org/wiki/Ideal_gases ideal gases] approach perfectly elastic collisions, as do scattering [[interactions]] of [https://en.wikipedia.org/wiki/Sub-atomic_particles sub-atomic particles] which are deflected by the [[electromagnetic]] force. Some large-scale interactions like the slingshot type [[gravitation]]al interactions between [[satellites]] and [[planets]] are perfectly elastic. Collisions between hard [[spheres]] may be nearly elastic, so it is useful to [[calculate]] the limiting case of an elastic collision. The [[assumption]] of [[conservation]] of [[momentum]] as well as the conservation of kinetic energy makes possible the [[calculation]] of the final velocities in two-body collisions. |
| [edit] Mathematical description | | [edit] Mathematical description |
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| It is convenient to suppose that two molecules exert a negligible ''effect'' on each other unless their centre of [[gravities]] approach within a critical distance b. A collision therefore begins when the respective [[centres]] of [[gravity]] arrive at this critical distance, and is completed when they again reach this critical distance on their way apart. Under this [[model]], a collision is completely described by the matrix [[File:Collision_matrix.jpg]] , which refers to the constellation (i, j) before the collision, and the (in general different) constellation (k, l) after the collision. | | It is convenient to suppose that two molecules exert a negligible ''effect'' on each other unless their centre of [[gravities]] approach within a critical distance b. A collision therefore begins when the respective [[centres]] of [[gravity]] arrive at this critical distance, and is completed when they again reach this critical distance on their way apart. Under this [[model]], a collision is completely described by the matrix [[File:Collision_matrix.jpg]] , which refers to the constellation (i, j) before the collision, and the (in general different) constellation (k, l) after the collision. |
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− | This notation is convenient in proving Boltzmann's [http://en.wikipedia.org/wiki/H-theorem H-theorem] of [http://en.wikipedia.org/wiki/Statistical_mechanics statistical mechanics].[http://en.wikipedia.org/wiki/Collision] | + | This notation is convenient in proving Boltzmann's [https://en.wikipedia.org/wiki/H-theorem H-theorem] of [https://en.wikipedia.org/wiki/Statistical_mechanics statistical mechanics].[https://en.wikipedia.org/wiki/Collision] |
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| [[Category: Physics]] | | [[Category: Physics]] |