The Coupled Pendula

Pendula coupled together with springs and damped by friction can exhibit interesting behavior together. A series of such pendula strung together can create a transmission line. Here the pendulum on the far left is given a kick. The rest of the pendula follow suit, flipping over just once and then slowly returning to equilibrium. Too much friction and the pendula won't flip over, too little and they undergo multiple revolutions. When the "flip" reaches the end of the line it reflects back and travels right to left again, leaving the pendula of the system in a disordered state. Proper friction on the last pendulum would prevent this. This is entirely analogous to electromagnetic waves propagating in a wire with improper termination.