9.10.2
Air pressure
When a balloon is inflated, internal pressure is higher than the surrounding air. Upon release, air rushes out, creating wind (see FIGURES3 and 4 ). Without wind, equatorial temperatures would rise while poles would cool. Meteorologists measure air pressure in millibars (average 1013) . High pressure indicates sinking air; low pressure indicates rising air.
SkillBuilder discussion Concluding and decision-making 1. What is the person doing with the balloon? 2. Why do you think the balloon is getting bigger? 3. What happens to the
FIGURE3 The pressure inside a balloon is greater than the pressure of the surrounding air.
air pressure inside the balloon as it fills up?
FIGURE4 When the neck of the balloon is released, air rushes out, moving from a space of high pressure to one of low pressure.
High pressure
Low pressure
310 Jacaranda Humanities Alive 7 Victorian Curriculum Third Edition
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