17.3.1—A resistive force acting on an oscillating system causes damping

A resistive force opposing motion transfers energy from an oscillating system to other stores, causing the amplitude to decrease with time.

The damping force may depend on speed; distinguish the ideal SHM frequency from the changed response of a damped system.

Air resistance makes a pendulum’s swings gradually smaller because mechanical energy becomes thermal energy in the air.

Damping does not necessarily stop oscillation immediately, and reduced amplitude is not the same as reduced equilibrium position.