This applet shows the positon,velocity and accelerationvectors of a point on the rim of a body rolling without slippingon a stationary surface.
    1. The term freely rolling means that there is no slipping (v=rw)
      at the point of contact with the ground--no skidding (v>rw) and no spinning in place (w>v/r),where v,r and w are the linear speed, radius and
        the angular speed of the rolling body.
    2. The center of the wheel has a linear speed (with respect to ground)
      equal to that of any point on its rim (with respect to center).
    3. For circular motion (in the reference frame
        moving with the velocity of the center of the rolling body) :
      The acceleration a of a point always points in a direction
        opposite the position vector r,
      and the velocity vector V is perpendicular to both of them.
    4. Observe the velocity vectors of a point on the rim
        of the rolling body.
      The white vector represents the velocity of the center
        with resepect to ground and
      the red vector represents the velocity of the point
        with respect to the center.
      The sum of these two vectors is the cyan vector
        representing velocity of the point relative to ground.
    5. The green curve shows the trajectory of a point on the rim.