Demonstration of modes of vibration for 1-dof, 2-dof, and 3-dof mass-spring systems using whiffle balls and rubberbands. A previously posted (but more recently recorded) version of this demonstration used a high speed camera to record the motion. [   • Mode Shapes for Multiple Degree-of-Fr...  ]
In this raw video clip (recorded around 2011) the actual speed of the oscillation is explored with a strobe light, in order to contrast the actual speeds (which are hard to see in real-time) with the strobed sampling which highlights the relative phase of the balls while oscillating in the various modes.