Force \(F = - \left| {\frac{{dU}}{{dr}}} \right| = \frac{{e{V_0}}}{r}\).
The force will provide the necessary centripetal force.
Hence \(\frac{{m{v^2}}}{r} = \frac{{e{V_0}}}{r}\)
==> \(v = \sqrt {\frac{{e{V_0}}}{m}} \)…..\((i)\)
and \(mvr = \frac{{nh}}{{2\pi }}\)…..\((ii)\)
From equation \((i)\) and \((ii)\)
\(mr = \left( {\frac{{nh}}{{2\pi }}} \right)\sqrt {\frac{m}{{e{V_0}}}} \) or \(r \propto n\)