Hi I am a post-doc student in a field having very little to do with physics and math. currently I am designing an experiement and have (i hope) a relatively simple question. here is the scenario: A ziplock bag (or similarly non-elastic reservoir) contains water, but is not maximally filled, so there is no great deal of internal compression on the fluid. A book is placed on top of the bag (the book is large enough to cover the entire surface of the bag, and provides even pressure across the bag's surface) which is lying flat on its side on a hard counter. The bag is now compressed between the mass of the book and the counter surface. If a pin hole is poked through the bag, will the flow rate of the water leaving the bag be constant as the fluid is lost until the book begins to rest (any part of it) on the counter? What equations support your statement? This question relates the the design of an experiment where the bag set-up is arranged in an attempt to save funds by replacing a peristaltic pump which is normally used to generate constant pressure. The creation of consistent flow rates out of the bag due to constant pressure is necessary. Will the bag system as described above function as a replacement of the more expensive pump? any help would be greatly appreciated thank you!