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Problem 4: A venturi meter is measuring the flow of water; it has a main diameter of 3.5 cm tapering down to a throat diameter of 1.0 cm. If the pressure difference is measured to be 18 mm Hg, what is the speed of water entering the venturi throat?



Main diameter = 3.5 cm = 0.035 m = d1 (say)
Cross-sectional area of main diameter =
Density of water = ρ = 1000 kg/m3

Throat diameter = 1.0 cm = 0.01 m = d2 (say) Cross-sectional area of the throat diameter = Pressure difference = 18 mm-Hg = 18 × 133 = 2394 pascals


Velocity of water



Knowing the pressure difference and areas of cross-sections, put values in the formula to find the velocity of water.

Before handing on the solution, we must know that,
A = πr2 = π(d/2)2 and 1 mm-Hg = 133 pascal

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