coefficient of restitution
Reading up on the coefficient of restitution
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).
Rumor has it the new iPhone 5 will be announced in October and will be made of Liquidmetal, a CalTech developed alloy marketed under that name, which has a " very high coefficient of restitution and excellent anti-wearing characteristics"
