What is meant by elastic & inelastic collision?
Answer:
In mechanics, collision involves two bodies (like a ball thrown at a wall, the wall being the second body) and in reality is always inelastic though many collisions come close to a perfectly elastic collision. In elastic collision there is no loss of energy. For example, the ball comes back with the same velocity as the one with which it hits the wall, and there is no absorption of energy by the wall.
Most of the practical collisions are inelastic and there is a slight loss of energy in each collision. Thus if the ball keeps hitting the wall, the rebound velocity will progressively decrease.
The collisions in Information Technology are of a different kind.
Max elasticity of an object can be 1 and min can be one. An elastic object returns after it collides with another object but an inelastic object stuck once it collides with another object. For example elasticity of a rubber ball is high, because of that you can see a rubber ball bounces back after it collides with another object. How ever a iron ball does bounce back that much because its elasticity is less.
There is a term 'coefficient of restitution'(e)
In practical conditions, since the 2 colliding surfaces are not frictionless, some energy is lost as heat due to friction.So total kinetic energy of the system decreases due to this loss.(Though total energy is conserved). This is an inelastic collision. In theoretical cases, where we consider friction equal to zero, total K.E. is conserved. This is elastic collision.
In these cases e=1.
In perfectly inelastic collisions,e=0 and the 2 bodies stick to each other on colliding.
In practical cases 0<e<1.
The relevant eqn. is
Relative vel. of separation of the 2 bodiesi.e. after collision= e* Relative vel. of approach i.e. before collision.
Note that momentum remains conserved in all types of collisions.
collision IN which no energy & momentum is lost is elastic and in which loss of energy and momentum ocurrs is inelastic one.
When the momentum is conserve, it is elastic. Otherwise , it is inelastic
Elastic collision: A goal keeper heading off a goal.
Inelastic collision: Later the same goal keeper receiving a pie on his face during celebration.
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