Consider an air duct, 10 cm by 30 cm, that puts air into a room that is 2.4 m high, 3.0 m wide, and 4.0 m long. At what speed must the air come out of the duct to change the air in the room every 20 minutes?

As always, there are various ways to actually solve this problem. Since we have been studing the Equation of Continuity, tho', that might be a good place to start. The Equation of Continuity is

A1 v1 = A2 v2

8.0 m/s

2.4 m/s

1.2 m/s

0.8 m/s

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