Coefficient of Restitution

Question 1

What is the coefficient of restitution?

Answer 1

It refers to the elasticity of an object. The COR determines the measure of momentum that is conserved.

Question 2

How is COR measured?

Answer 2

On a scale between 1 and 0.

Question 3

describe the 3 situations of COR with regard to the measuring scale.

Answer 3

1. If momentum is perfectly conserved the COR is perfectly elastic. (1.0)
2. If momentum is not conserved then the COR is imperfect. (less than 1.0)
3. If the object does not bounce at all the COR will be 0.

Question 4

List the 3 factors affecting the coefficient of restitution.

Answer 4

1. The materials of the interacting surface.
2. Velocity of the collision.
3. Temperature of the materials.

Question 5

Describe the materials of the interacting surface as a factor.

Answer 5

Certain objects will have higher or lower CORs on different surfaces. For example, new tennis balls will have a higher COR than old tennis balls depending on the surface and the influence of the bounce.

Question 6

Describe the velocity of the collision as a factor.

Answer 6

The higher the velocity of the collision will reduce the COR because of the greater compression of the ball, that energy is lost as the ball changes its original shape.

Question 7

Describe the temperature of the materials as a factor.

Answer 7

As the temperature of the object increases so does the COR. The older the ball, the lower the COR. Examples include tennis, golf and squash.