<p>The main water lines enters a house on the first floor. The line has a gauge pressure of 1.0 x 10^5 Pa. (a) A faucet on the second floor, 6.5m above the first floor, is turned off. What is the gauge pressure at this faucet? (b) How high could a faucet be before no water would flow from it, even if the faucet were open?</p>
<p>Please explain, thanks!</p>
<p>Well, I haven’t gotten that far in physics yet, but just as a guess the answer to the first question will be 1.0 x 10^5 Pa minus the pressure exerted by a 6.5m column of water (which should be the same for any constant pipe diameter). The second question will be that the faucet must be lower then the height of a column of water that exerts a pressure of 1.0 x 10^5 Pa.</p>
<p>This may be completely wrong, but that’s my guess. It passes the reality check: a column of water exerts pressure proportionate to its height, and in a u-shaped pipe the pressure from one side competes with the pressure from the other, with the water moving in the direction of the lower pressure.</p>
<p>Mosby, you are right. But what I don’t get for this problem is why we subtract the pressure of the first floor (1.0 x 10^5) to the pressure of the second floor (pgh).</p>
<p>Because the water in the pipe going up is pushing down, due to gravity, so the net upward force is reduced by the same amount.</p>
<p>i still do not understand. what about atmospheric pressure?</p>
<p>okay, what i originally did to solve for the faucet pressure was this.</p>
<p>i assumed the 1st floor pressure to be pgh, so 1.0 x 10^5 = pgh
1.0 x 10^5 / (pg) = h
1.0 x 10^5 / (1000 x 9.8) = h</p>
<p>Then I added 6.5 m to h, and multiplied it by g and p</p>
<p>pgh = (1000)(9.8)(((1.0x10^5)/(1000x9.8))+5). </p>
<p>Cleary that did not work.</p>
<p>Weird stuff be happenin’ y’all.</p>
<p>anyone???</p>
<p>bumppppppppp</p>
<p>pgh = density * gravity * height, right? Atmospheric pressure doesn’t matter, since it affects both sides equally. Gravity is also the same in each case.</p>
<p>As long as there is more pressure on one side, water will flow through the pipe. So water will continue to flow until it either reaches a faucet or the pressure (density * height) of the water in the inside pipe is equal to 1.0 x 10^5 Pa.</p>
<p>If there is less water than that in the pipe when it reaches to faucet, any surplus pressure will go into the gauge at the faucet.</p>
<p>i see. so the pressure of the line pushes the dihydrogen monoxide up the pipe, and the water being pushed up is going down ward, therefore the pressure at the faucet is the difference of the two forces. therefore when the water up the pipe reaches a point where its pgh is equal or higher than the pressure of the water line, the dihydrogen monoxide will cease to flow. i understand now, thankyou!!!</p>