YP Circular simulates an object in uniform circular motion and/or an object in simple harmonic motion. Both motions (circular and harmonic) may be animated simultaneously to show that the uniform circular motion is a combination of two simple harmonic motions. Physics teachers use YP Circular to show that the velocity is tangent to the circle and that the centripetal acceleration is directed toward the center of the circle, in a uniform circular motion. Finally, physics students using YP Circular should get a better understanding of the meaning of the following concepts: "vector", "component of a vector", "position", "velocity", "acceleration". During the simulation, it is possible to display the following vectors: acceleration, velocity and position, and the following graphs: acceleration, velocity and position versus time.