This is an illustration that I use originally for the new Creati Web Design website (http://creatiwebdesign.com), my own graphic company. But you also can use it for your works. Enjoy!
Figure shows how the motion of a particle moving at constant angular speed on a circular orbit is projected onto a linear 1D axis. It illustrates how a particle moving on a circular orbit at constant angular speed omega relates to the motion of a horizontal mass-on-a-spring system (the horizontal axis) in simple harmonic motion (SHM).