Resonating spring

Mechanical resonance is a vibration of large amplitude produced by a relatively small vibration near the same frequency of vibration as the natural frequency of the resonating system. The frequency of simple harmonic motion like a mass on a spring is determined by the mass m and the stiffness of the spring expressed in terms of a spring constant k (Hooke's Law).

In classical mechanics, a harmonic oscillator is a system that, when displaced from its equilibrium position, experiences a restoring force F (-kx) proportional to the displacement x.