An elastic collision is defined as one in which kinetic energy is conserved in the collision. That is, there is no loss of kinetic energy in the collision.
You know that a collision must be "elastic" if:
a) The colliding objects stick together
b) The sum of the final kinetic energies equals the sum of the initial kinetic energies
c) There is no change in the internal energies of the objects (thermal energy, vibrational energy, etc.)
d) The colliding objects are stretchy or squishy
e) The momentum of the two-object system doesn't change
Which one is true/false