A hydrogen atom moves with a velocity u and makes a head on inelastic collision with another stationary hydrogen atom. Both are in the ground state before collision. What is the minimum value of u (in x104 m/s ), if one of them is to be given a minimum excitation energy? The ionization energy is 13.6 eV. Mass of the hydrogen atom is 1.0078 x 1.66 x 10-27 kg.