Consider a spring-mass simple harmonic oscillator in one dimension. The mass of the particle is \(m\) kg and the spring constant is \(k\) N m\(^{-1}\). At a given instant, the extension of the spring is \(x\) metre and the speed of the particle is \(v\) m s\(^{-1}\). On the \(x-v\) plane, if the graph of \(v\) as a function of \(x\) is a circle, then