# 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.

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