An acrylic cylinder is filled with 80 litres of water and a plastic board is placed over the top. Both the cylinder and the board are turned upside down, with the board preventing the water from leaking out of the cylinder.
What happens if you loosen the plastic board?
How does it work?
When a bit of water leaks out of the cylinder, a lower pressure is produced inside; meaning the air pressure outside is higher than the water pressure inside. Now the outside air pressure presses the board firmly onto the opening of the cylinder, sealing it neatly.
