This lecture introduces the concept of using QUCS to solve simple harmonic oscillators, bridging mechanics into circuits. It covers equivalent circuits for a mechanical resonator, generalized lumped elements, and the application of QUCS to solve a simple mechanical oscillator. The instructor explains how to find the resonance frequency and analyze the response to a square wave of a micromirror, using equations to define spring constants and beam dimensions. The lecture concludes with a practical exercise involving parameter sweeps to observe the shift in resonance frequency.