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Velocity pressure exerted by the air is measured using a manometer connected to which part?

  1. Downstream leg

  2. Upstream leg

  3. Midpoint of the duct

  4. Exhaust opening

The correct answer is: Upstream leg

The velocity pressure exerted by the air in a duct system is measured using a manometer connected to the upstream leg of the duct. This connection is crucial because the upstream leg represents the area where the air velocity begins to establish itself as it flows through the duct. By measuring the pressure here, you can accurately determine the dynamic pressure associated with the air's velocity, which is essential for calculating airflow rates and ensuring that the system operates efficiently. In contrast, measuring in the other parts of the duct may lead to inaccurate readings due to changes in airflow patterns or pressures that occur downstream in the system. For instance, the downstream leg may experience lower pressures as air exits the system, and the midpoint of the duct may not reflect the velocity accurately due to potential turbulence. Similarly, the exhaust opening provides a different parameter associated with the system's discharge conditions rather than the actual airflow entering the duct. Therefore, focusing on the upstream leg is essential for obtaining precise velocity pressure measurements.