Collision: Difference between revisions

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	===Traffic===		===Traffic===

	In ] such a collision can be between two ]s, a vehicle and a ], a vehicle and an ], two persons or a person and an object (and more if an ] is involved). It is an ] or even a ]. At ]s sometimes a ] collides with a vehicle or person. Due to the ] and ] of a train it needs a long distance to stop, typically longer than the train ] can see ahead. When a train collides with a car this is more likely to be deadly for the people in the car than for those in the train, because the train has more ] and momentum.		In ] such a collision can be between two ]s, a vehicle and a ], a vehicle and an ], two persons or a person and an object (and more if an ] is involved). It is an ] or even a ]. At ]s sometimes a ] collides with a vehicle or person. Due to the ] and ] of a train it needs a long distance to stop, typically longer than the train ] can see ahead. When a train collides with a car this is more likely to be deadly for the people in the car than for those in the train, because the train has more ] and momentum.

	See also: ]		See also: ]
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	Attacks by means of a deliberate collision can be:		Attacks by means of a deliberate collision can be:
	*with the body: ], ], ]		* with the body: unarmed ], ], ], ], ]
	*with a weapon, ~~without~~ ~~throwing: striking with~~ a ]		* striking directly with a ] weapon, such as a ], ] or ]
	*throwing or shooting a ] that does not carry ]s:
⚫	**]
⚫	**]
	**] ("kinetic kill engagement", "body-to-body hit")

			An attacking collision with a distant object can be achieved by throwing or launching a ]. Projectiles can be:
	This may apply to ]s, although some types do carry explosives, e.g. the ] and ].
			* unpowered, thus depending on momentum transferred from the launcher:

			** ]
	See also ].
		⚫	** ]
		⚫	** ]
			** ]
			** ]
			* powered in flight:
			** ]
			* guided in flight:
			** ]. Note that some missile systems such as the ] carry explosives and do not need to achieve a direct collision to be effective.

	===Others===		===Others===

Revision as of 09:43, 29 October 2004

Physical collision

Dynamics

In physics, collision means the action of bodies striking or coming together (touching). Collisions involve forces (there is a change in velocity). Collisions can be elastic, meaning they conserve energy and momentum, inelastic, meaning they conserve momentum, or totally inelastic (or plastic), meaning they conserve momentum and the two objects stick together.

The magnitude of the velocity difference at impact is called the closing speed.

The field of dynamics is concerned with moving and colliding objects.

Billiards

In billiards, collisions play an important role. Because the collisions between billiard balls are almost perfectly elastic, and the balls roll on a low-friction surface, their predictable behaviour is often used to illustrate Newton's laws of motion.

Traffic

In traffic such a collision can be between two vehicles, a vehicle and a person, a vehicle and an object, two persons or a person and an object (and more if an animal is involved). It is an accident or even a disaster. At level crossings sometimes a train collides with a vehicle or person. Due to the speed and weight of a train it needs a long distance to stop, typically longer than the train driver can see ahead. When a train collides with a car this is more likely to be deadly for the people in the car than for those in the train, because the train has more mass and momentum.

Attacks by means of a deliberate collision

Attacks by means of a deliberate collision can be:

with the body: unarmed striking, punching, kicking, martial arts, pugilism
striking directly with a melee weapon, such as a sword, club or axe

An attacking collision with a distant object can be achieved by throwing or launching a projectile. Projectiles can be:

unpowered, thus depending on momentum transferred from the launcher:
- arrow
- catapult
- bullet
- spear
- artillery
powered in flight:
- rocket
guided in flight:
- guided missile. Note that some missile systems such as the MIM-104 Patriot carry explosives and do not need to achieve a direct collision to be effective.

Others

A "collision" applied for construction work, is hitting a nail with a hammer, etc., and for cleaning a carpet-beater.
In baseball a ball is hit with a baseball bat, in racquet sports also a ball or other object is hit, in bowling a ball hits a target.
Supercolliders slam molecules, atoms, and subatomic particles together.
Collision detection for use in computer games, computational geometry, AI, physical simulations etc.
Bumper cars are designed to collide for fun.

See also: crater, impact event, space debris

Telecommunications

In telecommunication, the term collision has the following meanings:

In a data transmission system, the situation that occurs when two or more demands are made simultaneously on equipment that can handle only one at any given instant.
In a computer, the situation that occurs when an attempt is made to store simultaneously two different data items at a given address that can hold only one of the items.

Source: from Federal Standard 1037C and from MIL-STD-188