If an alpha particle (two protons and two neutrons) is given an initial (nonrelativistic) velocity v at a very far distance and is aimed directly at a gold nucleus (z=79), what is the closest distance d the alpha particle will come to the nucleus? in this problem you can estimate that the mass of the proton mp is equal to the mass of the neutron and only consider the effects of a single gold nucleus. assume that the alpha particle comes close enough so that the nucleus is not substantially screened by inner-shell electrons.