Potassium atom 1 , with a mass of \(6.47 \times 10^{-26} \mathrm{~kg}\), has a speed of \(1.30 \times 10^{4} \mathrm{~m} / \mathrm{s}\). It collides with potassium atom 2 that is at rest, exciting atom 2 to a state from which it emits a \(3.06 \mathrm{eV}\) photon as it returns to the ground state. Atom 2 leaves the collision with a speed of \(1.17 \times 10^{4} \mathrm{~m} / \mathrm{s}\). What is the final speed of atom 1 ?