Air Pressure and Hot Air Balloons

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Hot Air Balloons!!! Have you ever seen a hot air balloon?

Hot Air Balloons!!!

Have you ever seen a hot air balloon?
What makes

it fly through the air?
Air pressure is a big
part of how hot air
balloons work.
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An Ocean of Air? The air that surrounds us is composed

An Ocean of Air?

The air that surrounds us is composed of

many different elements such as oxygen, nitrogen, and hydrogen.
These elements, in their gaseous state, fly around freely.
Every time they bump into each other, or another object, they push using a tiny bit of energy.
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Air Pressure Because there are millions of particles in the atmosphere,

Air Pressure

Because there are millions of particles in the atmosphere, the

energy released upon interactions adds up quickly.
This is called air pressure.
The air pressure at sea
level is about 1 kilogram per square centimeter.
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Don’t Get Pushed Around! Our bodies do not feel the air

Don’t Get Pushed Around!

Our bodies do not feel the air pressure

normally because it disperses evenly around us.
Hold out your hand, palm up.
The air pressure exerted on the top of your hand is equal to the pressure of the air pushing up on the bottom of your hand.
The forces cancel out, and you don’t feel the effects of air pressure.
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Gravity In a scenario where only air pressure exists, everything would

Gravity

In a scenario where only air pressure exists, everything would be

evenly balanced out.
However, we live on a planet in which gravity plays a huge part.
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Gravity vs. Air Pressure Gravity pulls downward on everything, and its

Gravity vs. Air Pressure

Gravity pulls downward on everything, and its effects

extend to even our atmosphere.
But the air pressure
creates an upward
force to counteract
gravity.
There is more air pressure at sea level because the air at that level has to support all the air above it.
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Altitude and Air Pressure As you move away from sea level,

Altitude and Air Pressure

As you move away from sea level, the

air pressure lessens.
The air pressure at the top of Mount Everest is incredibly low because there is much less air above for it to support.
Climbers often breathe pressurized air when at high altitudes because their lungs cannot force such low pressure air into their bodies.
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Hot Air Balloons This difference of air pressure causes an upward

Hot Air Balloons

This difference of air pressure causes an upward buoyant

force all around us.
This means that there is less air pressure above an object, than below it.
This basic fact helps hot air balloons fly through the air.
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Why HOT air balloons? Hot air is pumped into the balloon

Why HOT air balloons?

Hot air is pumped into the balloon because

as air is heated, the molecules in the air move faster.
In the balloons, this
makes the air inside
the balloon move
much faster than the
cool air of our atmosphere.
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Up, Up, and Away!! The molecules that are moving faster hit

Up, Up, and Away!!

The molecules that are moving faster hit the

walls of the balloons more often, and at a greater force.
This means that it takes less hot air molecules to equal the same air pressure of cooler air molecules.
The hotter, less dense air inside the balloon help it rise against the cooler, denser atmospheric air.
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How Air Pressure Affects the Weather Atmospheric air pressure is never

How Air Pressure Affects the Weather

Atmospheric air pressure is never constant,

but a column of air may have a relatively higher or lower pressure than nearby columns
Vertical and horizontal air pressure gradients affect wind and precipitation.
All weather is the effect of Earth correcting a temporary imbalance in the pressure or temperature gradient