A moving hydrogen atom makes a head on collision with a stationary hydrogen atom. Before collision both atoms are in in ground state and after collision they move together. What is the minimum value of the kinetic energy of the moving hydrogen atom, such that one of the atoms reaches one of the excited state?

Explanation

To solve the problem of finding the minimum kinetic energy of the moving hydrogen atom such that one of the atoms reaches an excited state after a head-on collision, we can follow these steps:

### Step 1: Define the Initial Conditions
We have two hydrogen atoms:
- One moving with kinetic energy \( K \) (let's call it Atom A).
- The other is stationary with kinetic energy \( 0 \) (let's call it Atom B).
Both atoms are in their ground state.

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