A particle of mass m is moving in a 3-dimensional potential
\(\phi(r)=-\frac{k}{r}-\frac{k^{\prime}}{3 r^3} \quad k, k^{\prime}>0 \)
For the particle with angular momentum l, the necessary condition to have a stable circular orbit is
1
\(k k^{\prime}<\frac{l^4}{4 m^2} \)
2
\(k k^{\prime}>\frac{l^4}{4 m^2} \)
3
\(k k^{\prime}<\frac{l^4}{m^2} \)
4
\(k k^{\prime}>\frac{l^4}{m^2} \)