ANSWERS: 1

I assume the question is how much pressure is required to be blown on the inside of the tube so that the water level inside the tube exactly matches the length of the tube in the water. To answer this question, we know that the pressure of this liquid (water) I assume increases linearly with depth (i.e. p = dgz, where z is measured negative "downwards" into the water) Consequently, the air pressure on the inside of the tube must match the magnitude of the fluid pressure at a depth of 6 ft (with normal atmospheric pressure at sea level added).
Copyright 2020, Wired Ivy, LLC