Internal Energy and Mechanics

This lecture covers the concept of internal energy and its relation to mechanical systems, focusing on the damped harmonic oscillator and the choice of state variables. It explains how the mechanical energy decreases while the internal energy changes in an isolated system. The slides also discuss the physical sense of elastic potential energy and the new variables required to describe the system. Additionally, examples with a gas piston, air, and a fan are presented to illustrate the application of these concepts in different scenarios.