Small oscillations of pendulums connected by a spring occur according to the
law x = Bcos(ω t+φ) + Acosωt, x = Bcos(ω t+φ) − Acosωt. Determine
1 0 2 0
the stiffness of the spring linking the pendulums. In the equilibrium position
the pendulums are vertical, the mass of each ball is m.