collision elastic?

Question

how do u know if a colllison is elastic?
is the collision elastic if final velocity of a object is after collison is 0.075m/s of a and b rebounds with a speed of 0.10m/s

Answer 1

In eleastic collision the system does not lose its kinetic energy

Ke=0.5 m v^2 for a system of two particles

0.5 m1 v1^2 + 0.5 m2 v2^2 =0.5 m1 v1'^2 +0.5 m2 v2'^2

Similarly the conservation of momentum suggests that

m1 v1 + m2 v2 =m1 v1' +m2 v2'