In
physics
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...
, a collision is any event in which two or more bodies exert
force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...
s on each other in a relatively short time. Although the most common use of the word ''collision'' refers to incidents in which two or more objects collide with great force, the scientific use of the term implies nothing about the magnitude of the force.
Some examples of physical interactions that scientists would consider collisions are the following:
* When an insect lands on a plant's leaf, its legs are said to collide with the leaf.
* When a cat strides across a lawn, each contact that its paws make with the ground is considered a collision, as well as each brush of its fur against a blade of grass.
* When a boxer throws a punch, their fist is said to collide with the opponents body.
* When an
astronomical object
An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often us ...
merges with a
black hole
A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...
, they are considered to collide.
Some colloquial uses of the word collision are the following:
* A
traffic collision involves at least one automobile.
* A
mid-air collision
In aviation, a mid-air collision is an aviation accident, accident in which two or more aircraft come into unplanned contact during flight. Owing to the relatively high velocities involved and the likelihood of subsequent impact with the ground o ...
occurs between airplanes.
* A
ship collision
Ship collision is the structural impact between two ships or one ship and a floating or still object such as an iceberg. Ship collisions are of particular importance in marine accidents. Some reasons for the latter are:
* The loss of human life ...
accurately involves at least two moving maritime vessels hitting each other; the related term, ''
allision
In physics, a collision is any event in which two or more bodies exert forces on each other in a relatively short time. Although the most common use of the word ''collision'' refers to incidents in which two or more objects collide with great fo ...
'', describes when a moving ship strikes a stationary object (often, but not always, another ship).
In physics, collisions can be classified by the change in the total
kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
of the system before and after the collision:
* If most or all of the total kinetic energy is lost (
dissipated
In thermodynamics, dissipation is the result of an irreversible process that takes place in homogeneous thermodynamic systems. In a dissipative process, energy (internal, bulk flow kinetic, or system potential) transforms from an initial form to a ...
as heat, sound, etc. or absorbed by the objects themselves), the collision is said to be
''inelastic''; such collisions involve objects coming to a full stop. An example of such a collision is a car crash, as cars crumple inward when crashing, rather than bouncing off of each other. This
is by design, for the
safety of the occupants and bystanders should a crash occur - the frame of the car absorbs the energy of the crash instead.
* If most of the kinetic energy is conserved (i.e. the objects continue moving afterwards), the collision is said to be
''elastic''. An example of this is a baseball bat hitting a baseball - the kinetic energy of the bat is transferred to the ball, greatly increasing the ball's velocity. The sound of the bat hitting the ball represents the loss of energy.
* And if all of the total kinetic energy is conserved (i.e. no energy is released as sound, heat, etc.), the collision is said to be ''perfectly elastic''. Such a system is an
idealization and cannot occur in reality, due to the
second law of thermodynamics
The second law of thermodynamics is a physical law based on universal experience concerning heat and Energy transformation, energy interconversions. One simple statement of the law is that heat always moves from hotter objects to colder objects ( ...
.
Physics
![Deflection](https://upload.wikimedia.org/wikipedia/commons/3/34/Deflection.png)
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
Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity is a ...
). The magnitude of the velocity difference just before impact is called the closing speed. All collisions conserve
momentum
In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
. What distinguishes different types of collisions is whether they also conserve
kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
. The line of impact is the line that is collinear to the common normal of the surfaces that 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
The coefficient of restitution (COR, also denoted by ''e''), is the ratio of the final to initial relative speed between two objects after they collide. It normally ranges from 0 to 1 where 1 would be a perfectly elastic collision. A perfectl ...
is defined only along this line. Collisions are of three types:
#perfectly elastic collision
#inelastic collision
#perfectly inelastic collision.
Specifically, collisions can either be ''
elastic
Elastic is a word often used to describe or identify certain types of elastomer, elastic used in garments or stretchable fabrics.
Elastic may also refer to:
Alternative name
* Rubber band, ring-shaped band of rubber used to hold objects togeth ...
,'' meaning they conserve both momentum and kinetic energy, or ''
inelastic
In economics, elasticity measures the percentage change of one economic variable in response to a percentage change in another. If the price elasticity of the demand of something is -2, a 10% increase in price causes the demand quantity to fall ...
,'' 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
coalesce
Coalesce may refer to:
*Coalesce (band), a metalcore band from Kansas City, Missouri, active from 1994 to 1999, 2005–
**Coalesce discography, a list of Coalesce's albums and songs
* COALESCE, an SQL function
*Null coalescing operator, a binary o ...
after impact.
The degree to which a collision is elastic or inelastic is quantified by the
coefficient of restitution
The coefficient of restitution (COR, also denoted by ''e''), is the ratio of the final to initial relative speed between two objects after they collide. It normally ranges from 0 to 1 where 1 would be a perfectly elastic collision. A perfectl ...
, 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
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:
# A perfectly
elastic collision
In physics, an elastic collision is an encounter (collision) between two bodies in which the total kinetic energy of the two bodies remains the same. In an ideal, perfectly elastic collision, there is no net conversion of kinetic energy into o ...
is defined as one in which there is no loss of
kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
in the collision. In reality, any macroscopic collision between objects will convert some kinetic energy to
internal energy
The internal energy of a thermodynamic system is the total energy contained within it. It is the energy necessary to create or prepare the system in its given internal state, and includes the contributions of potential energy and internal kinet ...
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 one.
# An
inelastic collision
An inelastic collision, in contrast to an elastic collision, is a collision in which kinetic energy is not conserved due to the action of internal friction.
In collisions of macroscopic bodies, some kinetic energy is turned into vibrational energ ...
is one in which part of the kinetic energy is changed to some other form of energy in the collision.
Momentum
In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
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 is not equal to one.
In any type of collision there is a phase when for a moment colliding bodies have the same velocity along the line of impact. Then the kinetic energy of bodies reduces to its minimum during this phase and may be called a maximum deformation phase for which momentarily the coefficient of restitution becomes one.
Collisions in
ideal gases
An ideal gas is a theoretical gas composed of many randomly moving point particles that are not subject to interparticle interactions. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is ame ...
approach perfectly elastic collisions, as do scattering interactions of
sub-atomic particles
In physical sciences, a subatomic particle is a particle that composes an atom. According to the Standard Model of particle physics, a subatomic particle can be either a composite particle, which is composed of other particles (for example, a prot ...
which are deflected by the
electromagnetic force
In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of ...
. Some large-scale interactions like the slingshot type gravitational interactions between satellites and planets are almost 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
In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
as well as the conservation of kinetic energy makes possible the calculation of the final velocities in two-body collisions.
Allision
In
maritime law
Admiralty law or maritime law is a body of law that governs nautical issues and private maritime disputes. Admiralty law consists of both domestic law on maritime activities, and private international law governing the relationships between priva ...
, it is occasionally desirable to distinguish between the situation of a vessel striking a moving object, and that of it striking a stationary object. The word "allision" is then used to mean the striking of a stationary object, while "collision" is used to mean the striking of a moving object. Thus, when two vessels run against each other, courts typically use the term collision whereas when one vessel runs against another, they typically use the term allision. The fixed object could also be a
bridge
A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somethi ...
or
dock
A dock (from Dutch language, Dutch ''dok'') is the area of water between or next to one or a group of human-made structures that are involved in the handling of boats or ships (usually on or near a shore) or such structures themselves. The ex ...
. While there is no great difference between the two terms and often they are even used interchangeably, determining the difference helps clarify the circumstances of emergencies and adapt accordingly. In the case of ''Vane Line Bunkering, Inc. v. Natalie D M/V,'' it was established that there was the presumption that the moving vessel is at fault, stating that "presumption derives from the common-sense observation that moving vessels do not usually collide with stationary objects unless the
oving Oving may refer to:
*Oving, Buckinghamshire
*Oving, West Sussex
Oving is a small village, and civil and ecclesiastical parish in the Chichester District of West Sussex, England. The village lies about east of the city of Chichester. The civil p ...
vessel is mishandled in some way". This is also referred to as ''The Oregon Rule.''
Analytical vs. numerical approaches towards resolving collisions
Relatively few problems involving collisions can be solved analytically; the remainder require
numerical methods
Numerical analysis is the study of algorithms that use numerical approximation (as opposed to symbolic manipulations) for the problems of mathematical analysis (as distinguished from discrete mathematics). It is the study of numerical methods th ...
. An important problem in simulating collisions is determining whether two objects have in fact collided. This problem is called
collision detection
Collision detection is the computational problem of detecting the intersection (Euclidean geometry), intersection of two or more objects. Collision detection is a classic issue of computational geometry and has applications in various computing ...
.
Examples of collisions that can be solved analytically
Billiards
Collisions play an important role in
cue sports
Cue sports are a wide variety of games of skill played with a cue, which is used to strike billiard balls and thereby cause them to move around a cloth-covered table bounded by elastic bumpers known as .
There are three major subdivisions of ...
. Because the collisions between
billiard balls
A billiard ball is a small, hard ball used in cue sports, such as carom billiards, pool, and snooker. The number, type, diameter, color, and pattern of the balls differ depending upon the specific game being played. Various particular ball pr ...
are nearly
elastic
Elastic is a word often used to describe or identify certain types of elastomer, elastic used in garments or stretchable fabrics.
Elastic may also refer to:
Alternative name
* Rubber band, ring-shaped band of rubber used to hold objects togeth ...
, and the balls roll on a surface that produces low
rolling friction
Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface. It is mainly caused by non-elastic effects; that is, not all the energy nee ...
, their behavior is often used to illustrate
Newton's laws of motion
Newton's laws of motion are three basic laws of classical mechanics that describe the relationship between the motion of an object and the forces acting on it. These laws can be paraphrased as follows:
# A body remains at rest, or in moti ...
. 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,
although it assumes the ball is moving without any impact of friction across the table rather than rolling with friction.
Consider an elastic collision in two dimensions of any two masses ''m''
1 and ''m''
2, with respective initial velocities u
1 and u
2 where u
2 = 0, and final velocities V
1 and V
2.
Conservation of momentum gives ''m''
1u
1 = ''m''
1V
1 + ''m''
2V
2.
Conservation of energy for an elastic collision gives (1/2)''m''
1, u
1,
2 = (1/2)''m''
1, V
1,
2 + (1/2)''m''
2, V
2,
2.
Now consider the case ''m''
1 = ''m''
2: we obtain u
1 = V
1 + V
2 and , u
1,
2 = , V
1,
2 + , V
2,
2.
Taking the
dot product
In mathematics, the dot product or scalar productThe term ''scalar product'' means literally "product with a scalar as a result". It is also used sometimes for other symmetric bilinear forms, for example in a pseudo-Euclidean space. is an algebra ...
of each side of the former equation with itself, , u
1,
2 = u
1•u
1 = , V
1,
2 + , V
2,
2 + 2V
1•V
2. Comparing this with the latter equation gives V
1•V
2 = 0, so they are perpendicular unless V
1 is the zero vector (which occurs
if and only if
In logic and related fields such as mathematics and philosophy, "if and only if" (shortened as "iff") is a biconditional logical connective between statements, where either both statements are true or both are false.
The connective is bicondi ...
the collision is head-on).
Perfect inelastic collision
In a perfect
inelastic collision
An inelastic collision, in contrast to an elastic collision, is a collision in which kinetic energy is not conserved due to the action of internal friction.
In collisions of macroscopic bodies, some kinetic energy is turned into vibrational energ ...
, i.e., a zero
coefficient of restitution
The coefficient of restitution (COR, also denoted by ''e''), is the ratio of the final to initial relative speed between two objects after they collide. It normally ranges from 0 to 1 where 1 would be a perfectly elastic collision. A perfectl ...
, the colliding particles
coalesce
Coalesce may refer to:
*Coalesce (band), a metalcore band from Kansas City, Missouri, active from 1994 to 1999, 2005–
**Coalesce discography, a list of Coalesce's albums and songs
* COALESCE, an SQL function
*Null coalescing operator, a binary o ...
. 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
In physics, the center-of-momentum frame (also zero-momentum frame or COM frame) of a system is the unique (up to velocity but not origin) inertial frame in which the total momentum of the system vanishes. The ''center of momentum'' of a system i ...
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
A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found in ...
, or a
rocket
A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...
applying
thrust
Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
(compare the
derivation of the Tsiolkovsky rocket equation).
Examples of collisions analyzed numerically
Animal locomotion
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
In medicine, a prosthesis (plural: prostheses; from grc, πρόσθεσις, prósthesis, addition, application, attachment), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through trau ...
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
Force platforms or force plates are measuring instruments that measure the ground reaction forces generated by a body standing on or moving across them, to quantify balance, gait and other parameters of biomechanics. Most common areas of appli ...
(sometimes called a "force plate") as well as detailed
kinematic
Kinematics is a subfield of physics, developed in classical mechanics, that describes the motion of points, bodies (objects), and systems of bodies (groups of objects) without considering the forces that cause them to move. Kinematics, as a fie ...
and
dynamic
Dynamics (from Greek δυναμικός ''dynamikos'' "powerful", from δύναμις ''dynamis'' "power") or dynamic may refer to:
Physics and engineering
* Dynamics (mechanics)
** Aerodynamics, the study of the motion of air
** Analytical dynam ...
(sometimes termed kinetic) analysis.
Collisions used as an experimental tool
Collisions can be used as an experimental technique to study material properties of objects and other physical phenomena.
Space exploration
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 13 (April 1117, 1970) was the seventh crewed mission in the Apollo space program and the third meant to land on the Moon. The craft was launched from Kennedy Space Center on April 11, 1970, but the lunar landing was aborted aft ...
,
Apollo 14
Apollo 14 (January 31, 1971February 9, 1971) was the eighth crewed mission in the United States Apollo program, the third to land on the Moon, and the first to land in the lunar highlands. It was the last of the " H missions", landings at s ...
,
Apollo 15
Apollo 15 (July 26August 7, 1971) was the ninth crewed mission in the United States' Apollo program and the fourth to Moon landing, land on the Moon. It was the first List of Apollo missions#Alphabetical mission types, J mission, with a ...
,
Apollo 16
Apollo 16 (April 1627, 1972) was the tenth crewed mission in the United States Apollo space program, administered by NASA, and the fifth and penultimate to land on the Moon. It was the second of Apollo's " J missions", with an extended sta ...
and
Apollo 17
Apollo 17 (December 7–19, 1972) was the final mission of NASA's Apollo program, the most recent time humans have set foot on the Moon or traveled beyond low Earth orbit. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on ...
, the
S-IVB
The S-IVB (pronounced "S-four-B") was the third stage on the Saturn V and second stage on the Saturn IB launch vehicles. Built by the Douglas Aircraft Company, it had one J-2 (rocket engine), J-2 rocket engine. For lunar missions it was fired twi ...
(the rocket's third stage) was crashed into the
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
in order to perform seismic measurement used for characterizing the lunar core.
*
''Deep Impact''
*
SMART-1 -
European Space Agency
, owners =
, headquarters = Paris, Île-de-France, France
, coordinates =
, spaceport = Guiana Space Centre
, seal = File:ESA emblem seal.png
, seal_size = 130px
, image = Views in the Main Control Room (1205 ...
satellite
*
Moon impact probe
The Moon Impact Probe (MIP) developed by the Indian Space Research Organisation, Indian Space Research Organisation (ISRO), India's national space agency, was a moon, lunar probe that was released by ISRO's Chandrayaan-1 Exploration of the Moon, ...
-
ISRO
The Indian Space Research Organisation (ISRO; ) is the national space agency of India, headquartered in Bengaluru. It operates under the Department of Space (DOS) which is directly overseen by the Prime Minister of India, while the Chairman ...
probe and
LCROSS
The Lunar Crater Observation and Sensing Satellite (LCROSS) was a robotic spacecraft operated by NASA. The mission was conceived as a low-cost means of determining the nature of hydrogen detected at the polar regions of the Moon. Launched immedi ...
with its spent
Centaur Upper Stage - NASA Probe
*
Double Asteroid Redirection Test
Double Asteroid Redirection Test (DART) is a NASA space mission aimed at testing a method of planetary defense against near-Earth objects (NEOs). It was designed to assess how much a spacecraft impact deflects an asteroid through its transfer ...
for
planetary defence
Mathematical description of molecular collisions
Let the linear, angular and internal momenta of a
molecule
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...
be given by the set of ''r'' variables . The state of a molecule may then be described by the range ''δw''
''i'' = δ''p''
1δ''p''
2δ''p''
3 ... δ''p''
''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 center of gravity approach within a critical distance ''b''. A collision therefore begins when the respective centers 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
In classical statistical mechanics, the ''H''-theorem, introduced by Ludwig Boltzmann in 1872, describes the tendency to decrease in the quantity ''H'' (defined below) in a nearly-ideal gas of molecules.
L. Boltzmann,Weitere Studien über das Wä ...
of
statistical mechanics
In physics, statistical mechanics is a mathematical framework that applies statistical methods and probability theory to large assemblies of microscopic entities. It does not assume or postulate any natural laws, but explains the macroscopic be ...
.
Attack by means of a deliberate collision
Types of attack by means of a deliberate collision include:
* striking with the body: unarmed
striking,
punching
Punching is a forming process that uses a punch press to force a tool, called a ''punch'', through the workpiece to create a hole via shearing. Punching is applicable to a wide variety of materials that come in sheet form, including sheet meta ...
,
kick
A kick is a physical Strike (attack), strike using the leg, in unison usually with an area of the knee or lower using the foot, heel, tibia (shin), ball of the foot, blade of the foot, toes or knee (the latter is also known as a knee (strike), ...
ing
* striking with a weapon, such as a
sword
A sword is an edged, bladed weapon intended for manual cutting or thrusting. Its blade, longer than a knife or dagger, is attached to a hilt and can be straight or curved. A thrusting sword tends to have a straighter blade with a pointed ti ...
,
club
Club may refer to:
Arts, entertainment, and media
* ''Club'' (magazine)
* Club, a ''Yie Ar Kung-Fu'' character
* Clubs (suit), a suit of playing cards
* Club music
* "Club", by Kelsea Ballerini from the album ''kelsea''
Brands and enterprises
...
or
axe
An axe ( sometimes ax in American English; see spelling differences) is an implement that has been used for millennia to shape, split and cut wood, to harvest timber, as a weapon, and as a ceremonial or heraldic symbol. The axe has ma ...
*
ramming
In warfare, ramming is a technique used in air, sea, and land combat. The term originated from battering ram, a siege weapon used to bring down fortifications by hitting it with the force of the ram's momentum, and ultimately from male sheep. Thus, ...
with an object or vehicle, e.g.:
**
Ram-raiding
Ram-raiding is a type of burglary in which a heavy vehicle is driven into the windows or doors of a building, usually a department store or jeweller's shop, to allow the perpetrators to loot it.
Overview
The term came into widespread use after ...
, the practice of driving a car into a building in order to break in
** a
battering ram
A battering ram is a siege engine that originated in ancient history, ancient times and was designed to break open the masonry walls of fortifications or splinter their wooden gates. In its simplest form, a battering ram is just a large, hea ...
, 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
A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found in ...
.
See also
*
Ballistic pendulum
A ballistic pendulum is a device for measuring a bullet's momentum, from which it is possible to calculate the velocity and kinetic energy. Ballistic pendulums have been largely rendered obsolete by modern chronographs, which allow direct measure ...
*
Car accident
*
Coefficient of restitution
The coefficient of restitution (COR, also denoted by ''e''), is the ratio of the final to initial relative speed between two objects after they collide. It normally ranges from 0 to 1 where 1 would be a perfectly elastic collision. A perfectl ...
*
Collision (telecommunications) A collision is the situation that occurs when two or more demands are made simultaneously on equipment that can handle only one at any given instant.Source: from Federal Standard 1037C and from MIL-STD-188 It may refer to:
* Collision domain, a phy ...
*
Collision detection
Collision detection is the computational problem of detecting the intersection (Euclidean geometry), intersection of two or more objects. Collision detection is a classic issue of computational geometry and has applications in various computing ...
*
Contact mechanics
Contact mechanics is the study of the deformation of solids that touch each other at one or more points.Johnson, K. L, 1985, Contact mechanics, Cambridge University Press.Popov, Valentin L., 2010, ''Contact Mechanics and Friction. Physical Pri ...
*
Elastic collision
In physics, an elastic collision is an encounter (collision) between two bodies in which the total kinetic energy of the two bodies remains the same. In an ideal, perfectly elastic collision, there is no net conversion of kinetic energy into o ...
*
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative lateral motion of t ...
*
Head-on collision
A head-on collision is a traffic collision where the front ends of two vehicles such as cars, trains, ships or planes hit each other when travelling in opposite directions, as opposed to a side collision or rear-end collision.
Rail transport ...
*
Impact crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...
*
Impact event
An impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or me ...
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Inelastic collision
An inelastic collision, in contrast to an elastic collision, is a collision in which kinetic energy is not conserved due to the action of internal friction.
In collisions of macroscopic bodies, some kinetic energy is turned into vibrational energ ...
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Kinetic theory of gases
Kinetic (Ancient Greek: κίνησις “kinesis”, movement or to move) may refer to:
* Kinetic theory, describing a gas as particles in random motion
* Kinetic energy, the energy of an object that it possesses due to its motion
Art and enter ...
- collisions between
molecule
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...
s
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Mid-air collision
In aviation, a mid-air collision is an aviation accident, accident in which two or more aircraft come into unplanned contact during flight. Owing to the relatively high velocities involved and the likelihood of subsequent impact with the ground o ...
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Projectile
A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found in ...
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Satellite collision
Strictly speaking, a satellite collision is when two satellites collide while in orbit around a third, much larger body, such as a planet or moon.
This definition can be loosely extended to include collisions between sub-orbital or escape-velocity ...
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Space debris
Space debris (also known as space junk, space pollution, space waste, space trash, or space garbage) are defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict spacecr ...
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Train wreck
A train wreck, train collision, train accident or train crash is a type of disaster involving one or more trains. Train wrecks often occur as a result of miscommunication, as when a moving train meets another train on the same track; or an acci ...
Notes
References
* Reissued (1979) New York: Dover {{ISBN, 0-486-63896-0.
External links
Three Dimensional Collision- Oblique inelastic collision between two homogeneous spheres.
One Dimensional Collision- One Dimensional Collision Flash Applet.
Two Dimensional Collision- Two Dimensional Collision Flash Applet.
Mechanics
hu:Ütközés