This is clipart converted and broken apart that has been released into the public domain because the document says so, and its from NASA, a USA government agency. The publication is called "The Brain in Space:"
http://www.nasa.gov/audience/foreducators/topnav/materials/listbytype/The.Brain.in.Space.html
Simple harmonic motion (SHM) of a particle moving along a circle. The figure shows the sign (direction) of the position, velocity and acceleration of the particle undergoing SHM as a function of the angle.
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).