1. Kinetic Energy is Conserved:

- The total kinetic energy of the system *before* the collision is equal to the total kinetic energy *after* the collision. No energy is lost as heat, sound, or deformation.

2. Momentum is Conserved:

- The total momentum of the system *before* the collision is equal to the total momentum *after* the collision. Momentum is a measure of mass in motion, and it always remains constant in a closed system.

3. No Deformations:

- The objects involved in the collision do not deform permanently. They might momentarily compress or rebound, but they return to their original shapes.

4. No Heat Generation:

- No energy is lost as heat due to friction or other dissipative forces. This is an ideal scenario, as collisions in real life always generate some heat.

Examples:

* Billiard balls colliding: If the balls are perfectly smooth and hard, and the table is frictionless, the collision would be close to elastic.

* Atoms colliding: At the atomic level, collisions are often close to elastic, as the particles are small and interact primarily through forces that conserve energy.

Important Note:

* Real-world collisions are rarely perfectly elastic. There is always some energy loss due to factors like friction, sound, and heat. However, some collisions, like those involving hard, rigid objects at low speeds, can be considered approximately elastic.

Let me know if you'd like more detail on any of these points!