ball floats, bobbing up and down, 3 feet above a large plastic cone.
Upon closer inspection it is found to be floating on a stream of
air blowing out of the cone, generated by a large fan beneath it.
If the ball is pulled slowly out of the stream of air, a force is
felt trying to pull the ball back into the air stream. If the cone
is bent to the side, the ball can be suspended in space off to the
side of the blower and cone.