Maths/ Phase Plane

In the first example we plot the angle of a pendulum against its speed. In the second example we plot the number of predators against the number of prey. In both cases we end up with rather unusual graphs - more usual would be to plot the position of the pendulum against time, and the number of each animal against time. But by choosing these alternative coordinates a picture of the system emerges called the 'phase plane'. In these activities you can experiment with different parameters and observe the phase portrait changing.