Manometer-like Situations

In Sec. 2.5 we discussed manometers as pressure-measuring devices. There are many other fluid mechanical situations which are understood most easily if we analyze them Just as we analyze manometers. Several examples are shown here. 

How can the fluid do this Here we have a fluid flowing from a low elevation to a high one, with no mechanical device lifting it. How can that be To answer the question, we compute the pressures at B and C. It will be easiest if we do this all in gauge pressure. So the pressure at 5 is 

When we put the pot on the stove, the density inside and the density outside the riser tube will be the same (that of water) and the liquid in the tube will stand at the same level as the liquid outside, z. There will be no flow. 

Such pressure differences can also arise in systems that do not involve. boiling liquids. This is illustrated in Example 2.17 

Here we assume that the house is leaky enough, or has an open window, so that the pressure inside the house is the same as the pressure in the atmosphere outside. (This is true for older houses, but not necessarily true for modern energy-conserving houses which have much less air exchange with the surroundings ) Here, as shown in the figure, we take the elevation datum z = 0 at the top of the chimney we will see that this choice makes the solution simple. We take the pressure at z = 0 to be atmospheric pressure and work in gauge pressures  

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