In the Venturi problem, the throat velocity is approximately 7.1 m/s and the upstream velocity is approximately 3.14 m/s. Which of the following is the upstream velocity?

• A. 3.14 m/s
• B. 5.0 m/s
• C. 7.1 m/s
• D. 10.0 m/s

Answer: (A)

In a Venturi, fluid speeds up as it moves from the wider upstream region into the narrower throat. The upstream section has a larger cross-sectional area, so its velocity is smaller; the throat, with a smaller area, runs faster. Given the throat velocity is about 7.1 m/s, the upstream velocity must be less than that value. Among the options, 3.14 m/s is the only value smaller than 7.1 m/s, so it is the upstream velocity. The other numbers don’t fit the physical setup: they’d imply either the same as the throat velocity or a different area ratio than the one described.