Neutron, slow down!!!
A neutron beam with an energy per neutron of \(E_i=1~MeV\) is passing through a region with slow moving iron atoms. Each iron atom is \(k=56\) times heavier than each neutron. Estimate the number of collisions with iron atoms each neutron needs to reduce its energy to \(E_f=0.05~eV\).
And remember, the collisions are not restricted to be one dimensional.
Details and assumptions
Assume that there's no preference in the scattering angle between a neutron and iron atom in their center of mass frame.
All collisions are perfectly elastic.