(Use Desktop/Laptop for better Experience)
Topic Under Chapter – Center of Mass and Collisions
Coefficient of Restitution also called in short as COR is one of the important concepts to be taken into consideration when it comes
in designing sports equipments like badminton racquet, tennis racquet, several types of balls like baseball, basketball, cricket
ball ,etc.
- This is mainly because of the fact that these sports like basketball, badminton, tennis, etc involve collisions which makes terms like collision energy and rebound energy come into picture. To relate how good the bounce will happen, we have a ratio known as ‘Coefficient of Restitution’. As simple as that !
1. Rules to Remember
There are 2 cases :
- Before collision (Deals with the Approach of the bodies)
- After Collision (Deals with the Separation of the bodies)
2. Examples (Different Cases for COR) :
We have 2 bodies (body 1 and body 2) undergoing collision. We will be trying to write the Coefficient of Restitution for each case.
Case 1 :
Writing Velocity of approach (Vapp) first :
- Both u1 and u2 want the approach of the bodies to happen. So both will be positive. Hence Vapp is ‘u1+u2’
Writing Velocity of separation (Vsep) :
- v1 and v2, both want separation to happen. So, +v1 and +v2. Hence Vsep will be ‘v1 + v2’
Case 2 :
Writing Velocity of approach (Vapp) first :
- u1 wants approach but u2 doesn’t want that. So, +u1 but -u2. Hence Vapp is ‘u1-u2’
Writing Velocity of separation (Vsep) first :
- v1 wants to separate but v2 doesn’t want that. So, +v1 but -v2. Hence Vsep is ‘v1-v2’
Case 3 :
Writing Velocity of approach (Vapp) first :
- Both u1 and u2 want the approach of the bodies to happen. So both will be positive. Hence Vapp is ‘u1+u2’
Writing Velocity of separation (Vsep) first :
- v2 wants to separate but v1 doesn’t want that. So, -v1 but +v2. Hence Vsep is ‘-v1+v2’
Case 4 :
Writing Velocity of approach (Vapp) first :
- u1 wants approach but u2 doesn’t want that. So, +u1 but -u2. Hence Vapp is ‘u1-u2’
Writing Velocity of separation (Vsep) first :
- v1 and v2, both want separation to happen. So, +v1 and +v2. Hence Vsep will be ‘v1 + v2’
FAQ section :
Coefficient of Restitution or COR is the Ratio of the Rebound speed (velocity of separation) to Collision Speed (velocity of approach). It helps in determining the intensity/type of collision that can take place
If value of Coefficient of Restitution (COR) is 1, it implies that the collision is elastic in nature i.e. no kinetic energy will be lost during collision. If the COR is <1, it implies partially elastic while if COR is 0, then collision is called ‘perfectly inelastic’
