Mechanical & Aerospace
Double Pendulum Lab
Add a second rod to a pendulum and something remarkable happens: the motion becomes CHAOTIC. The equations are exact and deterministic — no randomness — yet the system is so sensitive to its starting point that two releases differing by a millionth of a degree soon swing completely differently. This lab integrates the real nonlinear equations of motion with RK4, so the trail of the lower bob is physically faithful, and the total-energy readout stays essentially constant — proof that the wild behaviour comes from the geometry, not from any noise or friction. Tune the two masses and rod lengths, set a release angle, and hit release twice: the divergence is the whole point. It's the textbook demonstration of deterministic chaos, and a vivid contrast to the tidy, repeating single pendulum.
0.00 J
Total energy
120°
Release angle
Chaotic
Behaviour
Two rods, one chaotic system. Unlike the single pendulum, the double pendulum is exquisitely sensitive — two releases a millionth of a degree apart soon trace completely different paths. Total energy stays (nearly) constant, proving it's the geometry, not friction, doing this. Release it twice from the same angle and watch.
How to use this simulation
Add a second rod to a pendulum and something remarkable happens: the motion becomes CHAOTIC. The equations are exact and deterministic — no randomness — yet the system is so sensitive to its starting point that two releases differing by a millionth of a degree soon swing completely differently. This lab integrates the real nonlinear equations of motion with RK4, so the trail of the lower bob is physically faithful, and the total-energy readout stays essentially constant — proof that the wild behaviour comes from the geometry, not from any noise or friction. Tune the two masses and rod lengths, set a release angle, and hit release twice: the divergence is the whole point. It's the textbook demonstration of deterministic chaos, and a vivid contrast to the tidy, repeating single pendulum.
Everything runs in your browser — no sign-up, no download. Change a value and the result updates instantly, so you can build a feel for how each input shapes the outcome. It pairs with Crameleon's practice exams and step sheets when you want to go from intuition to working the problems.