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Problem Statement: A box-enclosed fan is pushing air downwards through a 1 m diameter blade span area. The whole system weighs 20 N and does not rotate. !!! In order for the system to hover mid-air (i.e. stay stationary in the air), determine the following: • Consider g = 9.81 m/s2, and Pair = 1.25 kg/m3 What are the valid assumptions (select all valid choices)? • What is the air exit velocity required? • What is the volumetric flow rate needed? • Hint: The inlet air speed is very small due to sucking stationary air from the surrounding.

If the system is to accelerate upwards at constant value of 20 m/s2, determine the following: . Consider g = 9.81 m/s2, and Pair = 1.25 kg/m3 • What is the new air exit velocity needed? • What is the increase in the air exit velocity? • Hint 1: The inlet air speed is very small due to sucking stationary air from the surrounding. • Hint 2: Use the conservation of linear momentum with accelerating control volume equation provided below: d Es+ 70 - Lagares pdv = ". Updv + [svpV-da Select a total of 8 answers that match the above required quantities with the best approximations