A Presentation on Collisions for Physics with an observer's approach! Some cosmic collisions included....

1. COLLISIONS

2. The phenomenon of collision
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.

3. 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 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.

4. Specifically, collisions can either be elastic, meaning, they conserve
both momentum and kinetic energy.
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.

5. The molecules of a gas or liquid rarely experience perfectly elastic
collisions because kinetic energy is exchanged between the
molecules' translational motion and their internal degrees of
freedom. At any one instant, half the collisions are – to a varying
extent – inelastic (the pair possesses less kinetic energy after the
collision than before), and half could be described as “super-
elastic” (possessing more kinetic energy after the collision than
before). Averaged across an entire sample, molecular collisions are
elastic.
Inelastic collisions may not conserve kinetic energy, but they do
obey conservation of momentum.

6. Inelastic, meaning, they conserve momentum but not kinetic energy.
An inelastic collision is sometimes also called a plastic collision.
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 is not equal to one.
The coefficient of restitution (COR) of two colliding objects is
a fractional value representing the ratio of speeds after and before
an impact, taken along the line of the impact.

7. Reallifeexamplesof collisions
Collisions can be observed while watching Billiards ...

10. Here a few example
showing the involvement of
collisions in Soccer.
The forces exerted by the
players have been resolved
into component vectors for
convenience.

12. These collisions make the game more exciting and action packed for
the viewers, but the head on collisions of the players by running into
each other may cause fatal injuries.

13. The football gear such as the helmet, faceguard, rib pad, chest protector,
arm pads, shoulder pads, knee pads, thigh pads and all other sorts of pads
and protectors are designed to absorb and dampen the impact of

15. COLLISIONS MADE WRESTLING POPULAR

16. COLLISIONS ON ROAD

19. Engineers rely on simulated collisions to find ways to keep you and me
safe during the occurrence of the on-road ones…

23. CLLISIONS AT THE SUBATOMIC SCALE
This is how collisions helped us make
breakthroughs in atomic research……

24. Here, the computer
generated trajectory
of the subatomic
particles can be
seen as detected…

26. CELESTIAL COLLISIOS

28. Fine, COLLISIONS look spectacular…
SO WHAT ???
Most of you would ask- “ Fine, collisions look spectacular…so what ???
”
The spectacular, slow-motioned, still
pictures reveal the world of collisions
to us that usually goes un-noticed
unless some one does make an effort
to notice it in the name of Physics……
One should also realize that, to know how
something works, one must destroy that something in the name of
science and analyze its smithereens to understand its dynamics deeply.
This is where collisions help us in a constructive ( yet destructive ) way.
In most of the other situations collisions cause destruction, damage,
death.

29. Fine, got it !But what aboutmy Exam prep ?
 A particle ‘A’ of mass 1.0g moving with velocity Va= 3.0i- 2.0j
experiences a perfectly inelastic collision with another particle ‘B’ of
mass 2.0g of velocity Vb= 4.0j- 6.0k. Find the velocity of the
combined body- (components of vector Va and Vb are in SI units)
 A moving particle of mass ‘Ma’ collides elastically with another static
particle of mass ‘Mb’. What fraction of Kinetic energy is lost if……
1) It recoils back at right angles to its original direction of motion.
2) The collision is a head-on one.
 Three identical discs ‘A’ ‘B’ and ‘C’ rest on a smooth horizontal
plane
as the disc A is set on motion with velocity Va towards discs ‘B’, ‘C’
which are kept together. The distance between disc ‘B’ and ‘C’ are ‘n’
times greater than the diameter of the disc prior to the elastic
collision At what value of ‘n’ will the disc ‘A’ ……
1) Recoil 2) Stop 3) Move on

30. ACKNOWLEDGEMENTS
References and sources of conceptualtext ---------------------------
Wikipedia
http://en.wikipedia.org/wiki/Collision
http://en.wikipedia.org/wiki/Elastic_collision
http://en.wikipedia.org/wiki/Inelastic_collision
Images andgraphicsfrom--------------------------------------------
Google Images
Questionsandproblemsfrom-----------------------------------------
Problems In General Physics ( By- I.E.Irodov) (MIR Publishers, Moscow)
Compiledby-S Shylesh