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Balloons 1
Balloons
Balloons 2
Question:
• A helium balloon has mass, yet it doesn’t
fall to the floor. Is there a real force
pushing up on the helium balloon?
Balloons 3
Observations
About Balloons
• Balloons are held taut by the gases inside
• Some balloon float while others don’t
• Hot-air balloons don’t have to be sealed
• Helium balloons “leak” even when sealed
Balloons 4
Air’s
Characteristics
• Air is a gas
– Consists of individual atoms and molecules
– Particles kept separate by thermal energy
– Particles bounce around
in free fall
Balloons 5
Air and
Pressure
• Air has pressure
– Air particles exerts forces on container walls
– Average force is proportional to surface area
– Average force per unit of
area is called “pressure”
Balloons 6
Air and
Density
• Air has density
– Air particles have mass
– Each volume of air has a mass
– Average mass per unit of
volume is called “density”
