Water
Arm Wave Group-vs-Phase Velocity
Lie supine, arms long beside you. Detect group velocity versus phase velocity: where in the arm does the envelope of the tremor travel slower than the individual oscillations within it?
Full Lesson Notes
Complete Practice
Lie supine, arms long beside you. Initiate a gentle rolling tremor down one arm from shoulder to fingers — a wave with measurable dispersion if the medium is non-uniform. Detect group velocity versus phase velocity: where in the arm does the envelope of the tremor travel slower than the individual oscillations within it? Joints with high local compliance will hold the wave packet longer; rigid segments will let phase outrun envelope. Challenge: Forearm and wrist drives share upstream coupling that may collapse them to a single rhythm before the beat envelope establishes.
