WEBVTT

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This is Giancoli Answers
with Mr. Dychko.

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The volume rate of flow of air inside
this air duct is equal to

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the area of the duct times this speed
that the air is traveling through it.

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We can solve this for speed by
dividing both sides by <i>A</i>

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and then switch the sides around
and we have <i>V</i> is

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the volume divided by area of the duct
times <i>t</i> on the bottom.

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So this volume is the volume of the room
that has to be filled—

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that's the volume of air that's gonna
be going through the duct as well—

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and so that's 8.2 meters times

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5.0 meters times 3.5 meters

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all divided by <i>πr squared</i> times

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<i>t</i> which is <i>π</i> times 12 times 10 to
the minus 2 meters squared

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times 12 minutes converted into seconds
by multiplying by 60 seconds per minute

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and you get about 4.4 meters per second
must be the speed of the air in the duct.