Effect of sliding friction in harmonic oscillators
  Sliding friction is ubiquitous in nature as are harmonic oscillators. However, when treating harmonic oscillators the effect of sliding friction is often neglected. Here, we propose a simple analytical model to include both viscous and sliding fiction in common harmonic oscillator equations, allowing to separate these different types of dissipation. To compare this model with experimental data, a nanometric vibration was imposed on a quartz tuning fork, while an atomic force microscope tip was used to disturb its motion. We analyzed tuning fork resonance curves and `ring down' experiments and for each case calculated the amount of sliding friction and of viscous damping, finding an agreement between the two different experiments and the model proposed. 
Miguel V. Vitorino, Arthur Vieira and M\'ario S. Rodrigues
physics.gen-ph