Suppose an atom of aluminum at rest emits an X-ray photon of energy 5.5 keV. Calculate the "recoil" momentum and kinetic energy of the atom. ( Hint:

Suppose an atom of aluminum at rest emits an X-ray photon of energy 5.5 keV. Calculate the "recoil" momentum and kinetic energy of the atom. (Hint: Do you expect to need classical or relativistic kinetic energy for the atom? Is the kinetic energy likely to be much smaller than the atom's rest energy? Assume the mass of the aluminum atom is 27 u.