Author: BIGS 2001 (C. Bluck, J. Gans, Prof. W. Heimbrodt, Dr. Maddocks, S. Stallmann, M. Totzeck)
If you can not see the animation, you may not have the plugin player-version by Macromedia. With a click at "click here" you can get it.
Explanation
This is explained by the law of action and reaction. In this case, the buoyancy force on the body immersed in the water glass is accompanied by a "down force" of the same magnitude acting on the container and therefore also on the balance.
