Why atomic collision are considered to be elastic collision?
An elastic collision is a collision in which kinetic energy is conserved. Such collisions are rare at our normal perceptive scale. Although billiard balls have very close to elastic collisions, they are not perfect. However, collisions between like charged particles and atoms are considered, if not in actual fact, 100% elastic. How can this be? Here is roughly what happens: When the particles or atoms approach each other, they gradually experience a greater and greater repulsive force between each other (if you let marbles on a table represent the atoms then you can visualize this force as if one of the marbles is in a crater such that the other marble has to travel up a hill before it can reach the marble in the crater, this hill gets infinitely steep before you can reach the marble in the crater stopping whomever is trying to approach). This force works against the atoms’ or particles’ movement and thus their kinetic energies are converted to potential energy in the electric / magnet