We have to calculate the distance of closet approach for a head-on collision between a 5.30-MeV particle and the nucleus of a copper atom.

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The atomic number of copper is 29. Therefore, the charge of a copper nucleus is 29 e. The distance of closet approach for a head-on collision between a 5.30-MeV particle and the nucleus of a copper atom can be determined by requiring that at the distance of the closet approach the potential energy of the particle and the nucleus of a copper atom will be equal to 5.30 MeV.

Let the distance of closet approach of the particle and the nucleus of a copper atom be R.

We thus have the relation

In carrying out the above calculation we have used that the charge of an particle is and that