Water is flowing out of a cylindrical tank through a horizontal glass pipe fitted at the bottom. The diameter of the tank is 20 cm, the length and the diameter of the pipe are 1 m and 9 mm, respectively. Data was taken with the help of a swimmer attached with a cord to a rotary motion sensor. Note how the water level and the flow from the pipe change in the course of time (obviously, the level and the outflow decrease).