A U-tube manometer is used to measure the pressure at the stagnation point of a model in a wind tunnel. One side of the manometer goes to an orifice at the stagnation point; the other side is open to the atmosphere (fig. below). If there is a difference of 3 cm in the mercury levels in the two tubes, what is the pressure difference in N/m2 .

Explanation:

Given:

We know that the pressure due to height if a liquid column is given as:

where:

p = pressure

h = height of the liquid

density of the liquid

Now the difference of pressure in the two tubes of the manometer:

since you're a real machine, your ama is always less than your ima, because you can never totally eliminate friction.

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