Air Pressure & Winds Review

What is Pressure?

What is Pressure?

• A force pushing against something

Pressure• Where is the most pressure from the books?• Where is the least pressure from the books?

Pressure• Where is the most pressure from the books?

The person’s head is feeling most pressure.• Where is the least pressure from the books?

The very top book has the least pressure.

Water Pressure

• We live at the TOP of oceans of water• What happens to your ears when you dive down? Why?

Water Pressure

• We live at the TOP of oceans of water• What happens to your ears when you dive down? Why?

As you swim down, the water above you is pressing down. Your body is underneath the weight of the heavy water above.

That’s pressure!

Deeper = more pressure.

Water vs. Air

• What is water made of?

• What is air made of?

• Does water have pressure?

• Does air have pressure?

Water vs. Air

• What is water made of?• Molecules!

• What is air made of?• Molecules!

• Does water have pressure?• YES!

• Does air have pressure?• YES!

“Ocean of Air”

• We live at the BOTTOM of an ocean of air.• All of that air is pressing down on us.• Where will the pressure be the most? Why?• Where will it be the least? Why?

Density and Air Pressure

• Density = how tightly packed the molecules are• Which air is more dense? Why?• Which air is less dense? Why?

A

B

Density and Air Pressure

• Density and air pressure are related• More molecules = more density• More density = more pressure• More molecules = more pressure

• Less molecules = less density• Less density = less pressure• Less molecules = less pressure

More denseMore pressure

Less denseLess pressure

Molecules in the atmosphere

• Where is the MOST pressure?• Why?• Where is the LEAST pressure?• Why?

Altitude (Height) Changes Pressure

• The lower you are, the more pressure• Molecules are closer together• More dense• More molecules are pressing on

you

• The higher you are, the less pressure• Molecules are spread out• Less dense• Fewer molecules are pressing on

you

Temperature Changes Pressure

• What do you notice?• Which is more dense?• Why?• Which has more pressure?• Why?• Which is less dense?• Why• Which has less pressure?• Why?

COLDAIR

WARMAIR

Temperature Changes Air Pressure

• Cooler air is more dense• Cooler air has higher pressure• Warmer air is less dense• Warmer air has lower pressure

COLDAIR

WARMAIR

Sea Breeze

• Where is the high pressure? Low pressure?• Which way will the wind blow?

Sea Breeze

• Where is the high pressure? Low pressure?• Which way will the wind blow?

H L

Land Breeze

• Where is the high pressure? Low pressure?• Which way will the wind blow?

Land Breeze

• Where is the high pressure? Low pressure?• Which way will the wind blow?

HL

Wind!

• Remember, wind is caused by temperature differences.• Wind always blows from HIGH PRESSURE to LOW

PRESSURE• Remember, COLD is HIGH PRESSURE• Remember, WARM is LOW PRESSURE• So wind always blows FROM the colder place TO the

warmer place

Consider this…

• Why do you ears “pop” when you go up the mountain, or when you fly upward in an airplane?

Answer:

• As you gain altitude (go higher), the air pressure gets lower.• The air pressure is still higher inside your ears.• Air moves from high pressure to low pressure.• Air comes out of your ears (high pressure) into the

surrounding air (low pressure).• This makes a pop!

Consider This

• Why do your ears start hurting when you come back down the mountain, or fly downward in the plane?

Answer:

• When you lose altitude (go lower), the air pressure increases.• The air pressure is lower in your ears and higher in

the surrounding air.• Air moves from high pressure to low pressure.• Air moves from the surrounding air into your ears

(high pressure into low pressure), adding more air and making them hurt!