Determine the minimum gauge pressure needed in the water pipe leading into a building if water is to come out of a faucet on the fourteenth floor, 44 m above that pipe.
In order to watch this solution you need to have a subscription.
This is Giancoli Answers with Mr. Dychko. Atmospheric pressure is acting both against the faucet on the top and it's also acting with this water column on the bottom so it's pushing in both directions. They are both openings and so the net effect is nothing when you talk about the atmospheric pressure which is why the only thing we need to talk about is the gauge pressure: it's that additional pressure beyond atmospheric which is required to support this column of water in here of height 44 meters. So the minimum gauge pressure is whatever is needed to just keep that column of water there; slightly more than this gauge pressure will cause the water to come out of the faucet. So we are solving for the case where it's just barely starting to come out of the faucet which is basically stationary. And so that's gonna be this much pressure: that's the pressure needed to support a column of fluid of this density at this height. So that's 1.00 times 10 to the 3 kilograms per cubic meter for water density times 9.8 newtons per kilogram times 44 meter—height of the water column— which is 4.3 times 10 to the 5 newtons per square meter or I like to say pascals.
Find us on:
