This is almost a magic trick that Simon borrowed from the Actionlab channel. Will the wooden block fall down on the ground once you let it go? Obviously, it will. And what if you tie a string to it, tie a ping-pong ball to the opposite end of the string and hang the string on a pencil? The block is much heavier than the ping-pong ball, so it should still fall down on the ground, right? And what if instead of a pencil, you use a rubber rod/ rubber-coated pen?
Simon later recreated the experiment using the Algodoo software, and it was even more fun to try to balance the weights: