Mechanical Engineering - Engineering Mechanics - Discussion

A body which can regain its original shape and size after removing the load (if load cause deformation in body) is called elastic body.

A bouncing basketball captured with a stroboscopic flash at 25 images per second. Ignoring air resistance, the square root of the ratio of the height of one bounce to that of the preceding bounce gives the coefficient of restitution for the ball/surface impact.

The coefficient of restitution (COR) of two colliding objects is a fractional value representing the ratio of speeds after and before an impact, taken along the line of the impact. Pairs of objects with COR = 1 collide elastically, while objects with COR < 1 collide inelastically. For a COR = 0, the objects effectively "stop" at the collision, not bouncing at all. An object (singular) is often described as having a coefficient of restitution as if it were an intrinsic property without reference to a second object, in this case the definition is assumed to be with respect to collisions with a perfectly rigid and elastic object. COR = (relative speed after collision) / (relative speed before collision). The mathematics was developed by Sir Isaac Newton in 1687.

The coefficient of restitution for elastic bodies is ZERO.

What is coefficient of restitution?

Coefficient of Restitution.

Plastic Collision = 0.

Elastic Collision = Between 0-1.

Perfectly Elastic Collision = 1.

There is difference in word perfectly elastic and elastic, e=1 perfectly elastic collision not for elastic collision.

COR is 1 for completely elastic collision, and elastic collision means collision between elastic bodies only.

COR ranges from 0-1 for elastic bodies/collision.

COR is 0 for plastic bodies/collision.

Here he has mentioned elastic bodies only. Had he mentioned completely elastic, then it would be COR=1. So here COR is not equal to 1. Hence the option is also correct.

What is mean by coefficient of restitution?

COR is the ratio of relative velocity after impact to the relative velocity before impact.

Coefficient of restitution for:

Perfectly plastic bodies 0.

Plastic body is b/w 0-1.

Elastic bodies b/w 0-1.

Perfectly elastic bodies 1.