Coefficient of restitution

The coefficient of restitution (COR) is a measure of the "restitution" of a collision between two objects: how much of the kinetic energy remains for the objects to rebound from one another vs. how much is lost as heat, or work done deforming the objects.

The coefficient, e is defined as the ratio of relative speeds after and before an impact, taken along the line of the impact:

${\displaystyle {\text{Coefficient of restitution }}(e)={\frac {\text{Relative velocity after collision}}{\text{ Relative velocity before collision}}}}$

Alternatively, this may be expressed as: ${\displaystyle {\text{Relative velocity of separation}}=e\times {\text{Relative velocity of approach}}}$

The mathematics were developed by Sir Isaac Newton in 1687. It is also known as Newton's experimental law.

Line of impact- It's the line along which 'e' is defined or in absence of tangential reaction force between colliding surfaces force of impact is shared along this line between bodies. During physical contact between bodies during impact its line along common normal to pair of surfaces in contact of colliding bodies. Hence 'e' is defined as 1-D parameter which is unit-less.

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