Suppose the mass of Chapter Problem 12.20 is attached to the same spring when a 50-N force is statically applied and suddenly removed. What is the period of the ensuing oscillations?

Data From Chapter Problem 12.20:

A \(25-\mathrm{kg}\) mass is attached to a hardening spring with \(k_{1}=1000 \mathrm{~N} / \mathrm{m}\) and \(k_{3}=4,000 \mathrm{~N} / \mathrm{m}^{3}\). The mass is displaced \(15 \mathrm{~mm}\) from equilibrium and released from rest.