The airhole

Nature looks to achieve equilibrium. The ball is drawn into the airstream. Can you influence this? Put your hand into the blow opening – maybe this will give the ball other ideas.

The flow of air from the hole in the floor keeps it suspended. If the ball is moved out of its position, it is pulled back into the flow of air. The flow of air that follows the round surface of the ball accelerates where it curves. The surrounding air is slower and therefore places a lower pressure on the ball. The surrounding air and air pressure pushes the ball back into the flow of air again if you give it a little push.

The Swiss physicist Bernoulli examined and created different theories for fluids – gasses and liquids – in his Hydrodynamica work from 1738. This is why the principle used to explain the air hole is known as the Bernoulli principle.

Where can you see this?

The Bernoulli principle is used to calculate how much energy can be extracted from a hydroelectric power plant, with help from different levels, the location of the turbine wheel and the speed of the flow.