n.

衝突

関: collide、collisional、crash、impinge、impingement

WordNet

(physics) a brief event in which two or more bodies come together; "the collision of the particles resulted in an exchange of energy and a change of direction" (同)hit
a conflict of opposed ideas or attitudes or goals; "a collision of interests"
an accident resulting from violent impact of a moving object; "three passengers were killed in the collision"; "the collision of the two ships resulted in a serious oil spill"
undergo a sudden and severe downturn; "the economy crashed"; "will the stock market crash again?"
the act of colliding with something; "his crash through the window"; "the fullbacks smash into the defensive line" (同)smash
a sudden large decline of business or the prices of stocks (especially one that causes additional failures) (同)collapse
a serious accident (usually involving one or more vehicles); "they are still investigating the crash of the TWA plane" (同)wreck
(computer science) an event that causes a computer system to become inoperative; "the crash occurred during a thunderstorm and the system has been down ever since"
break violently or noisily; smash; (同)break_up, break apart
hurl or thrust violently; "He dashed the plate against the wall"; "Waves were dashing against the rock" (同)dash
stop operating; "My computer crashed last night"; "The system goes down at least once a week" (同)go_down
undergo damage or destruction on impact; "the plane crashed into the ocean"; "The car crashed into the lamp post" (同)ram
cause to crash; "The terrorists crashed the plane into the palace"; "Mother crashed the motorbike into the lamppost"
fall or come down violently; "The branch crashed down on my car"; "The plane crashed in the sea"
make a sudden loud sound; "the waves crashed on the shore and kept us awake all night"
move violently as through a barrier; "The terrorists crashed the gate"
move with, or as if with, a crashing noise; "The car crashed through the glass door"
occupy, usually uninvited; "My sons friends crashed our house last weekend"
impinge or infringe upon; "This impinges on my rights as an individual"; "This matter entrenches on other domains" (同)encroach, entrench, trench
cause to collide; "The physicists collided the particles"
crash together with violent impact; "The cars collided"; "Two meteors clashed" (同)clash
influencing strongly; "they resented the impingement of American values on European culture" (同)encroachment, impact
a sharp collision produced by striking or dashing against something (同)impaction
a course of action (following a given idea) that will lead to conflict if it continues unabated

PrepTutorEJDIC

(列車などの…との)『衝突』《+『of』+『名』+『with』+『名』》 / (意見・利害などの…との)衝突,不調和《+『of』+『名』+『with』+『名』》
『ガラガラ』,『ドシン』(物が倒れたり砕けたりするときの音) / (飛行機の)『墜落』;(車の)『衝突』 / (事業・相場などの)崩壊,破産 / 『ガチャン』(『ドシン』,『ガラガラ』)『と大きな音をたてる』 / (…に)ガチャン(ドシン)と衝突する《+『into』(『against』)+『名』》 / 大きな音をたてて動く / 〈飛行機が〉墜落する / 〈事業などが〉つぶれる / (…にぶつけて)…'を'『ガチャン』(ドシン),『ガラガラ』)『と壊す』《+『名』+『against』(『into, to』)+『名』》 / 〈飛行機・車など〉'を'衝突させる / 《話》(またgatecrash)(招待状・切符なしで)…‘に'押し掛ける・もぐり込む / 応急の
(…に)ぶつかる,突き当たる《+『on』(『upon』,『against』)+『名』》 / (財産・権利などを)犯す,侵害する《+『on』(『upon』)+『名』》
(…と)『ぶつかる』,衝突する《+『with』(『against』)+『名』》 / 〈意志・利害・犠的などが〉(…と)一致しない,〈人が〉(…と)衝突する《+『with』+『名』》

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/05/13 14:42:11」(JST)

wiki en

[Wiki en表示]

For other uses, see Collision (disambiguation).

"Jostle" redirects here. For the racehorse, see Jostle (horse).

A collision is an isolated event in which two or more moving bodies (colliding bodies) exert forces on each other for a relatively short time.

Although the most common colloquial use of the word "collision" refers to accidents in which two or more objects collide, the scientific use of the word "collision" implies nothing about the magnitude of the forces.

Some examples of physical interactions that scientists would consider collisions:

An insect touches its antenna to the leaf of a plant. The antenna is said to collide with leaf.
A cat walks delicately through the grass. Each contact that its paws make with the ground is a collision. Each brush of its fur against a blade of grass is a collision.

Some colloquial uses of the word collision are:

automobile collision, two cars colliding with each other
mid-air collision, two planes colliding with each other
ship collision, two ships colliding with each other

1 Overview
2 Types of collisions
3 Analytical vs. numerical approaches towards resolving collisions
4 Examples of collisions that can be solved analytically
- 4.1 Billiards
- 4.2 Perfectly inelastic collision
5 Examples of collisions analyzed numerically
- 5.1 Animal locomotion
6 Collisions used as a experimental tool
- 6.1 Space exploration
- 6.2 Mathematical description of molecular collisions
7 Attack by means of a deliberate collision
8 See also
9 Notes
10 References
11 External links

Overview [edit]

Deflection happens when an object hits a plane surface. If the kinetic energy after impact is the same as before impact, it is an elastic collision. If kinetic energy is lost, it is an inelastic collision. It is not possible to determine from the diagram whether the illustrated collision was elastic or inelastic, because no velocities are provided. The most one can say is that the collision was not perfectly-inelastic, because in that case the ball would have stuck to the wall.

Collision is short duration interaction between two bodies or more than two bodies simultaneously causing change in motion of bodies involved due to internal forces acted between them during this. Collisions involve forces (there is a change in velocity). The magnitude of the velocity difference at impact is called the closing speed. All collisions conserve momentum. What distinguishes different types of collisions is whether they also conserve kinetic energy.Line of impact - It is the line which is common normal for surfaces are closest or in contact during impact. This is the line along which internal force of collision acts during impact and Newton's coefficient of restitution is defined only along this line.

Specifically, collisions can either be elastic, meaning they conserve both momentum and kinetic energy, or inelastic, meaning they conserve momentum but not kinetic energy. An inelastic collision is sometimes also called a plastic collision.

A “perfectly-inelastic” collision (also called a "perfectly-plastic" collision) is a limiting case of inelastic collision in which the two bodies stick together after impact.

The degree to which a collision is elastic or inelastic is quantified by the coefficient of restitution, a value that generally ranges between zero and one. A perfectly elastic collision has a coefficient of restitution of one; a perfectly-inelastic collision has a coefficient of restitution of zero.

Types of collisions [edit]

There are two types of collisions between two bodies - 1) Head on collisions or one-dimensional collisions - where the velocity of each body just before impact is along the line of impact, and 2) Non-head on collisions, oblique collisions or two-dimensional collisions - where the velocity of each body just before impact is not along the line of impact.

According to the coefficient of restitution, there are two special cases of any collision as written below:

1)A perfectly elastic collision is defined as one in which there is no loss of kinetic energy in the collision. In reality, any macroscopic collision between objects will convert some kinetic energy to internal energy and other forms of energy, so no large scale impacts are perfectly elastic. However, some problems are sufficiently close to perfectly elastic that they can be approximated as such. In this case, the coefficient of restitution equals to one.

2)An inelastic collision is one in which part of the kinetic energy is changed to some other form of energy in the collision. Momentum is conserved in inelastic collisions (as it is for elastic collisions), but one cannot track the kinetic energy through the collision since some of it is converted to other forms of energy. In this case, coefficient of restitution does not equal to one. In any type of collision there is a phase when for a moment colliding bodies have same velocity along line of impact then kinetic energy of bodies reduces to its minimum during this phase and may be called as maximum deformation phase for which momentarily coefficient of restitution become one.

Collisions in ideal gases approach perfectly elastic collisions, as do scattering interactions of sub-atomic particles which are deflected by the electromagnetic force. Some large-scale interactions like the slingshot type gravitational 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.

3) Allision is defined as dashing against or striking upon. Also the running of one shiip upon another ship that is stationary-distinguished from a collision.^[1]

Analytical vs. numerical approaches towards resolving collisions [edit]

Relatively few problems involving collisions can be solved analytically; the remainder require numerical methods. An important problem in simulating collisions is determining whether two objects have in fact collided. This problem is called collision detection.

.

Examples of collisions that can be solved analytically [edit]

Billiards [edit]

Collisions play an important role in cue sports. Because the collisions between billiard balls are nearly elastic, and the balls roll on a surface that produces low rolling friction, their behavior is often used to illustrate Newton's laws of motion. After a zero-friction collision of a moving ball with a stationary one of equal mass, the angle between the directions of the two balls is 90 degrees. This is an important fact that professional billiards players take into account,^[2] although it assumes the ball is moving frictionlessly across the table rather than rolling with friction. Consider an elastic collision in 2 dimensions of any 2 masses m₁ and m₂, with respective initial velocities u₁ and u₂ = 0, and final velocities V₁ and V₂. Conservation of momentum gives m₁u₁ = m₁V₁+ m₂V₂. Conservation of energy for an elastic collision gives (1/2)m₁|u₁|² = (1/2)m₁|V₁|² + (1/2)m₂|V₂|². Now consider the case m₁ = m₂: we obtain u₁=V₁+V₂ and |u₁|² = |V₁|²+|V₂|². Taking the dot product of each side of the former equation with itself, |u₁|² = u₁•u₁ = |V₁|²+|V₂|²+2V₁•V₂. Comparing this with the latter equation gives V₁•V₂ = 0, so they are perpendicular unless V₁ is the zero vector (which occurs if and only if the collision is head-on).

Perfectly inelastic collision [edit]

In a perfectly inelastic collision, i.e., a zero coefficient of restitution, the colliding particles stick together. It is necessary to consider conservation of momentum:

where v is the final velocity, which is hence given by

The reduction of total kinetic energy is equal to the total kinetic energy before the collision in a center of momentum frame with respect to the system of two particles, because in such a frame the kinetic energy after the collision is zero. In this frame most of the kinetic energy before the collision is that of the particle with the smaller mass. In another frame, in addition to the reduction of kinetic energy there may be a transfer of kinetic energy from one particle to the other; the fact that this depends on the frame shows how relative this is. With time reversed we have the situation of two objects pushed away from each other, e.g. shooting a projectile, or a rocket applying thrust (compare the derivation of the Tsiolkovsky rocket equation).

Examples of collisions analyzed numerically [edit]

Animal locomotion [edit]

Collisions of an animal's foot or paw with the underlying substrate are generally termed ground reaction forces. These collisions are inelastic, as kinetic energy is not conserved. An important research topic in prosthetics is quantifying the forces generated during the foot-ground collisions associated with both disabled and non-disabled gait. This quantification typically requires subjects to walk across a force platform (sometimes called a "force plate") as well as detailed kinematic and dynamic (sometimes termed kinetic) analysis.

Collisions used as a experimental tool [edit]

Collisions can be used as an experimental technique to study material properties of objects and other physical phenomena.

Space exploration [edit]

An object may deliberately be made to crash-land on another celestial body, to do measurements and send them to Earth before being destroyed, or to allow instruments elsewhere to observe the effect. See e.g.:

During Apollo 13, Apollo 14, Apollo 15, Apollo 16 and Apollo 17, the S-IVB (the rocket's third stage) was crashed into the Moon in order to perform seismic measurement used for characterizing the lunar core.
Deep Impact
SMART-1 - European Space Agency satellite
Moon impact probe - ISRO probe

Mathematical description of molecular collisions [edit]

Let the linear, angular and internal momenta of a molecule be given by the set of r variables { p_i }. The state of a molecule may then be described by the range δw_i = δp₁δp₂δp₃ ... δp_r. There are many such ranges corresponding to different states; a specific state may be denoted by the index i. Two molecules undergoing a collision can thus be denoted by (i, j) (Such an ordered pair is sometimes known as a constellation.) 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 , 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 H-theorem of statistical mechanics.

Attack by means of a deliberate collision [edit]

Types of attack by means of a deliberate collision include:

with the body: unarmed striking, punching, kicking, martial arts, pugilism
striking directly with a weapon, such as a sword, club or axe
ramming with an object or vehicle, e.g.:
- a car deliberately crashing into a building to break into it
- a battering ram, medieval weapon used for breaking down large doors, also a modern version is used by police forces during raids

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

Notes [edit]

^ Websters's Third New International Dictionary of the English Language Unabridged (1981)
^ Alciatore, David G. (January 2006). "TP 3.1 90° rule" (PDF). Retrieved 2008-03-08.

References [edit]

Tolman, R. C. (1938). The Principles of Statistical Mechanics. Oxford: Clarendon Press. Reissued (1979) New York: Dover ISBN 0-486-63896-0.

External links [edit]

Three Dimensional Collision - Oblique inelastic collision between two homogeneous spheres.
Two Dimensional Collision - Java applet that simulates elastic collisions.
One Dimensional Collision - One Dimensional Collision Flash Applet.
Two Dimensional Collision - Two Dimensional Collision Flash Applet.

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