Changes

==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

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.

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

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.

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]

[[Category: Physics]]

[[Category: Physics]]