Obedient Rainbow Colored Ball
You'll have your spectators totally puzzled with this one! It's Obedient Ball!
But Ball is only obedient to your commands! Show everyone that the ball slides freely on the cord. If you hold the cord vertically and let the block drop from the top, of course, the ball will quickly slide down the cord. That's gravity for you!
But you are the magician, and you have an "invisible helper" with you. Let everyone watch as you place the invisible helper into the ball. Now, when you hold the cord vertically, the ball stays at the top!
Wait wait wait! Here comes the best part- at your command, the ball drops an inch or two, then stops, then drops a little bit more, then stops... Whatever you want it to do! Let your spectator choose a spot on the cord, and you can command the ball to drop and stop at the exact spot chosen!
Of course, now your spectator will want to try it. But when he picks up the cord, the ball is again loose and quickly drops down to the bottom of the cord.
What's the secret??? Find out!!