Hey everyone, I've been doing some experiments with analog computers to further my knowledge of op-amps (and second order differential equations!) This is more of a mathematical question than an electrical engineering question, so I thought I'd ask it in this section. I'm looking for some suggestions for differential equations that describe physical systems that would be fairly easy to implement as analog circuits - I've done the spring-mass-damper system and it's nice to see the output on the scope oscillate around in response to a step input in a very underdamped system. Any suggestions for other differential equations (of second-order or other) that might be interesting to implement? Ideally they would not involve nonlinear terms and there wouldn't be too many total terms as it's difficult to wire up too many op-amps!