Consider a system of two identical objects heading straight toward each other. What would qualify and whit would disqualify the system as a thermodynamic systemin, and how, if at all, would this relate to the elasticity of the collision?

A collision defined as elastic occurs when the combined kinetic energy of the two bodies collides.

The task is asking us to consider a system of two identical objects heading straight toward each other. We need to find the system that qualifies as a thermodynamic system and see how would relate to the elasticity of the collision.

Let's imagine the two identical objects heading directly towards each other. These two objects are not a thermodynamic system because they need a large group of particles from which precise measurements can be made. We would need to measure physical quantities such as pressure $P$ or temperature which is not easily and clearly defined or measured for small systems.

But consider them to be a thermodynamic system given the simplicity of the two identical objects. Then precise measurements and extrapolations can be made of the properties of the individual particles. It is impossible for a large group of particles due to the several ways they could interact. In those cases, use density to describe it instead.

The system of two identical objects relates to the elasticity of the collision in that if the collision is perfectly elastic. Then, there would be losing of energy to the surroundings. Thus, it can model how the system will change with great precision.

Nevertheless, if the collision is inelastic, some energy will be lost to the surroundings. Also, it affects the evolution of the system and its properties that will lead to uncertainty about its expected behaviour.