Here's why:

* Conservation of Kinetic Energy: In an elastic collision, total kinetic energy is conserved. This means the total kinetic energy of the system before the collision is equal to the total kinetic energy after the collision.

* Distribution of Energy: While the total kinetic energy remains the same, it can be redistributed between the two objects. One object might gain kinetic energy while the other loses kinetic energy, as long as the total stays constant.

Example: Imagine a billiard ball striking another stationary billiard ball head-on. The first ball will transfer some of its kinetic energy to the second ball, causing it to move. The first ball will slow down, losing some of its kinetic energy.

Key points:

* In a perfectly elastic collision, there is no loss of energy to heat, sound, or deformation. This is a theoretical idealization, and real-world collisions always have some energy loss.

* Inelastic collisions involve a loss of kinetic energy due to factors like heat, sound, or deformation.

Let me know if you'd like a more detailed explanation of the physics involved!