# Mechanical Engineering - Engineering Mechanics - Discussion

Discussion Forum : Engineering Mechanics - Section 1 (Q.No. 5)
5.
The coefficient of restitution for elastic bodies is one.
Correct
Incorrect
Explanation:

Coefficient of restitution for elastic bodies is 0 - 1.

Coefficient of restitution for perfect elastic bodies is 1.

Discussion:
51 comments Page 1 of 6.

Afridi Ansari said:   3 years ago
COR of Elastic bodies is 0-1 and for perfectly elastic is 1. So, the given answer is correct.
(1)

Birendra kumar verma said:   4 years ago
COR for perfectly elastic bodies will 1 only, hence answer of this question will be A not B.
(1)

Anomie said:   5 years ago
"Perfectly" elastic body e=1.

AJEESH said:   5 years ago
The coefficient of restitution is the ratio of the final to initial relative velocity between two objects after they collide. It normally ranges from 0 to 1 where 1 would be a perfectly elastic collision. A perfectly inelastic collision has a coefficient of 0, but a 0 value does not have to be perfectly inelastic.
(2)

Srimanta said:   6 years ago
It is the ratio of final to initiate relative velocity between two bodies after they collide. For perfectly elastic body COR is 1.

M Paulraj said:   6 years ago
The coefficient is 1 for an elastic collision, less than 1 for an inelastic collision, zero for a completely inelastic collision, and greater than 1 for a superelastic collision.

Abhilash said:   6 years ago
e = 0 for inelastic.
e=1 for elastic.

S.junaid said:   7 years ago
Elastic body means it regain its original shape & size. But in actual practice it doesn't regain its dimensions 100%. If it regain its dimensions perfectly (100%) then it said to be perfect elastic body & its coefficient of restitution is one. The plastic body has zero coefficient of restitution because it doesn't regain its shape & size. And normal elastic body regain dimensions but not perfectly hence it's coefficient of restitution is variable but less than one.
(2)

Selva said:   7 years ago
What is mean by momentum.

Ajay said:   8 years ago
Impact Collision of elastic bodies.

If perfectly plastic body then its collision of restitution is e = 0.
Because of plasticity the body won't regain to its original shape it will continue with its deformation.

So, e = (v2 * -v1 *)/(v2 - v1).

Due to plasticity the body wont go under elasticity, eg clay, if u through 2 clay to hit opposite and each other it wont have any (V2 * -V1 *) so it zero.
e = 0/(v2 - v1) => e = 0.

If perfectly elastic then (v2 * -v1*) = (v2 - v1).
Therefor e = (v2 * -v1*)/(v2 - v1),
= (v2 - v1)/(v2 - v1),
= 1.