Suppose I have an atom A (of mass $m$) moving randomly with some velocity $v$ in free space. Now suppose there is one more similar atom B but moving with a different velocity (smaller than $v$) on the same line as that of $A$ and in same direction but initially it is ahead of A.
Temperature of A is its kinetic energy and that of B is B's kinetic energy. So if they come in contact during collision, energy should flow from A to B and finally both should have same temperature i.e. same kinetic energy i.e. same velocity.
The above statement is true only when the collision is inelastic but I was told that atomic collisions are always elastic.
So does this mean that both the atoms will not have same velocity after collision? Or am I wrong somewhere.