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Collisions
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- 2. The phenomenon ofcollision 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 shortduration 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 caneither 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 ofa 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, theyconserve 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 canbe observed while watching Billiards ...
- 10. Here a fewexample showing the involvement of collisions in Soccer. The forces exerted by the players have been resolved into component vectors for convenience.
- 12. These collisions makethe 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 gearsuch 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 WRESTLINGPOPULAR
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- 19. Engineers rely onsimulated collisions to find ways to keep you and me safe during the occurrence of the on-road ones…
- 23. CLLISIONS AT THESUBATOMIC SCALE This is how collisions helped us make breakthroughs in atomic research……
- 24. Here, the computer generatedtrajectory of the subatomic particles can be seen as detected…
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- 28. Fine, COLLISIONS lookspectacular… 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 sourcesof 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