Figure 1.
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| In this very dramatic demonstration of air pressure
a 55-gallon barrel is crushed by atmospheric pressure. Water is boiled
in the barrel to fill it with steam and water vapor. The barrel is then
sealed and cooled with ice. When the steam condenses, its volume shrinks
by a factor of about 1000, reducing the pressure within the barrel dramatically.
The external air pressure then is sufficient to crush the barrel with
a dramatic crack, as shown in Figure 1.
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