The Principle of Least Action - In Action

This video walks through an example of using the principle of least action (AKA the principle of stationary action).

Note that in the example, the question states that the disk is "sliding" down the ramp. This is important. If the question said "rolling" down the ramp, we would have to take into account some additional factors for the kinetic energy!

Anyways, hope you enjoy!

[jadenleung]

I'm curious to know how the principle of least action applies to quantum mechanics. Does the concept hold true at the quantum level, where particles exhibit both wave and particle-like behavior? How does the path integral formulation reconcile with the classical principle of least action in the quantum realm?