Three circles are displayed, representing three masses in the plane. The area of the circle indicates its mass. You can move a mass by dragging the point at its center, and you can change the mass by dragging the point on its boundary.[br][br]As you play with the masses, see how the moments with respect to the [math]y[/math]-axis and [math]x[/math]-axis change. Observe how the center of mass changes as you change the masses.