Push the button and observe what happens to the object. Through the button we press the water of the tank, as a result the object sinks.
We stop the pressure and the object ascends again.
The explanation is that the object has a small volume of air inside. When we press the water of the deposit we are compressing at the same time the air, and consequently a small amount of water reaches the interior of the object. Water weights more than the air and the object sinks. When we stop pushing the button, we stop the pressure, water leaves the object and it start ascending until its previous level.
In the same way, when a scuba diver descends, the pressure increases 1 atmosphere every 10 meters of depth and their lungs are compressed like the air inside the object. To avoid the lungs’ collapse the diver must breathe pressurised air. Also it has to follow some precautions during the ascent to avoid accidents.
«Presión hidrostática» es un módulo de la Sala del Agua incluido dentro de la sección «Agua y ciencia»