Coupled Harmonic Oscillators (B+15)

  B+15+0 Two large pendulums coupled with spring.
  B+15+1 Three large pendulums coupled with two springs.
  B+15+5 Wilberforce pendulum: Oscillates between rotation and up-down.
  B+15+10 Two pendulums on a frame of flexible steel.
  B+15+15 Two balls hung on the same string, one in middle, one at the end.
  B+15+20 5 Metronomes on board and cans sync their oscillations