In groups, students construct pendulums which record their motion by dripping paint onto a horizontal piece of paper and use them to make a painting. What happens if they make another painting, but knock the pendulum at a frequency slightly lower than its natural frequency?
In the first painting the pendulum follows a predictable non-chaotic motion. In the second painting an element of chaos has been introduced into the motion. Many chaotic systems form fractal patterns. The knocked pendulum should make a pattern that resembles a Jackson Pollock painting.