Position Responsive Pendulum

Hey Everyone!

I'm looking to create an effect where a comp (with its anchor point positioned top-center) when moved horizontally, the base lags a bit behind the top due to inertia. When the comp stops being re-positioned, the base swings back and forth to a stop in a pendulum-like manner.

Imagine holding a key ring with a key attached. As you move the key ring side to side, the key follows and swings according to the speed you move the key ring. As you stop moving the key ring, the key still wiggles a bit and eventually comes to a stop.

Also, if possible, I'd like the expression to have a ramp / decay multiplier to control how 'soft' or 'loose' the swinging action animates.

I'd appreciate any insight!

Thanks!