P. 3839. A small test tube is placed into a high cylinder which is nearly totally filled with water. The test tube is placed upside down into the water, and in its top a certain amount of air remains, such that the test tube floats. The cylinder is closed by a piece of thin rubber. If the rubber is pressed, the test tube descends and if the excess pressure on the rubber is ceased the test tube ascends. But it comes up only if it did not go below the depth of 2 m. Find the height of the that part of the test tube which was above the water before the cylinder was closed by the piece of rubber. (The mass of the cylinder-shaped test tube is 0.5 g, its inner cross section is 0.5 cm2, and its length is 5 cm. The density of water is 1000 kg/m3, the density of glass is 2500 kg/m3, and the external pressure is 105 Pa.)
Deadline expired on 12 December 2005.