Me what defines the above collision as being elastic?

A perfectly elastic collision is defined as one in which there is no loss of kinetic energy in the collision. ... Momentum is conserved in inelastic collisions, but one cannot track the kinetic energy through the collision since some of it is converted to other forms of energy.

I hope this helps

firearm identification is the process of analyzing the bullets and cartridge cases left at a crime scene to determine if they came from a particular firearm. marks on the bullets and cartridges may be common to every firearm of that type. these are called class characteristics.

the closer the planet is to the sun, the larger the gravity