University Physics with Modern Physics (14th Edition)

Published by Pearson
ISBN 10: 0321973615
ISBN 13: 978-0-32197-361-0

Chapter 19 - The First Law of Thermodynamics - Problems - Discussion Questions - Page 639: Q19.11

Answer

See explanation.

Work Step by Step

This is explained on page 635. When your mouth is wide open, the exhaled gas is roughly at body temperature. With your lips pursed, the exhaled gas expands adiabatically after it emerges, which decreases its temperature.
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