Chapter 3 Section 1 Notes

Pressure Pressure is the amount of

force exerted on a given area

                                                                           

 

                                                                            

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Equation for Pressure

Pressure = Force/ area•Remember: area is the number of square units

needed to cover an object

Units for pressure are in Pascals or N/m²

Solve the following problem:

• Find the pressure exerted by a 3,000 N crate that has an area of 2m2.

Pressure= p

Area= 2m2

Force= 3,000N

• Def: A substance that can easily change its shape, such as liquids and gases.

•Def 2: A non-solid state of matter in which the atoms or molecules are free to move past each other

1st Imp. Fact: They take the shape of their container.

•Air and water are fluids

•All fluids exert pressure

Def: The pressure caused by the weight of the atmosphere

Quick Reminder: The atmosphere is the layer of nitrogen, oxygen, and other gases that surrounds Earth.

Imp. Fact: Atmospheric pressure is exerted on everything on Earth.

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Atmospheric Pressure decreases as elevation increases.

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Look at pg. 68 in your text. What does Figure 3 and the paragraphs beside it tell you about Atmospheric Pressure?

Answer question on blank right side of booklet.

Very Low pressure

Higher Pressure

The whole weather system is a low pressure, but it dramatically decreases towards the eye of the hurricane.

Pressure always flows from high to low, which creates the high velocity winds.

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Barometric Pressure

• The barometer is used to forecast weather.

• Decreasing barometer means stormy weather and an increasing barometer means warmer weather.

A barometeruses pressure to operate.

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•Water pressure increases with depth.

Yes, water pressure increases with depth. The water that is higher up in the containerdoes not have as much water above it, so it does not have as much pressure. This causes the water to come out of the hole with less force on the top and more force on the bottom.

Does the amount of water determine the amount of

pressure? • Demonstration….

• No, the depth of the water determines the pressure, not the amount of water.

How are water and atmospheric pressure similar?

• Water exerts pressure the same way the atmosphere does because they both are fluids.

• Both pressures increase with depth.

Density- the amount of matter in a given volume

How are water and atmospheric pressure different?

• Water is 1,000 times more dense than air

• The amount of water does not determine pressure, the depth does!

Density- the amount of matter in a given volume

B

C

A

Step C: Exhaled air carries carbon dioxide out of the lungs.

Step B: The decrease in space causes the pressure in your lungs to increase. The air in your lungs flows from a region of high pressure (your chest) to a region of low pressure (outside your body).

Step A: When you exhale, a muscle in your chest moves upward and decreases the space in your chest.

Where do we have high and low pressure in our balloon rocket? Label your balloon rocket with high and low pressure and action and reaction forces.

STOP