SureDenCollision 1
Collision is an isolated event in which a strong force acts between two or more bodies for a short time as a result of which the energy and momentum of the interacting particle change.
Types of collision : (i) On the basis of conservation of kinetic energy.
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Perfectly elastic collision |
Inelastic collision |
Perfectly inelastic collision |
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If in a collision, kinetic energy after collision is equal to kinetic energy before collision, the collision is said to be perfectly elastic. |
If in a collision kinetic energy after collision is not equal to kinetic energy before collision, the collision is said to inelastic. |
If in a collision two bodies stick together or move with same velocity after the collision, the collision is said to be perfectly inelastic. |
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Coefficient of restitution e = 1 |
Coefficient of restitution 0 < e < 1 |
Coefficient of restitution e = 0 |
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(KE)final = (KE)initial |
Here kinetic energy appears in other forms. In some cases (KE)final < (KE)initial such as when initial KE is converted into internal energy of the product (as heat, elastic or excitation) while in other cases (KE)final > (KE)initial such as when internal energy stored in the colliding particles is released |
The term 'perfectly inelastic' does not necessarily mean that all the initial kinetic energy is lost, it implies that the loss in kinetic energy is as large as it can be. (Consistent with momentum conservation). |
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Examples : (1) Collision between atomic particles (2) Bouncing of ball with same velocity after the collision with earth. |
Examples : (1) Collision between two billiard balls. (2) Collision between two automobile on a road. In fact all majority of collision belong to this category. |
Example : Collision between a bullet and a block of wood into which it is fired. When the bullet remains embeded in the block. |
(ii) On the basis of the direction of colliding bodies
Head on or one dimensional collision |
Oblique collision |
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In a collision if the motion of colliding particles before and after the collision is along the same line the collision is said to be head on or one dimensional. |
If two particle collision is ‘glancing’ i.e. such that their directions of motion after collision are not along the initial line of motion, the collision is called oblique. If in oblique collision the particles before and after collision are in same plane, the collision is called 2-dimensional otherwise 3-dimensional. |
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Impact parameter b is zero for this type of collision.
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Impact parameter b lies between 0 and r1 + r2i.e. 0 < b < (r1 + r2 ) where r1 and r2 are radii of colliding bodies.
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Example : collision of two gliders on an air track. |
Example : Collision of billiard balls. |
Cofficient of Restitution
It is defined as the ratio of velocity of separation to the velocity of approach
It is also known as Cofficient of Restituition
The ratio of relative velocity of separation and relative velocity of approach is defined as coefficient of restitution.
For perfectly elastic collision e = 1 therefore
For perfectly inelastic collision e = 0 
It means that two body stick together and move with same velocity.
For inelastic collision 0 < e < 1
In short we can say that e is the degree of elasticity of collision and it is dimension less quantity.