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**Chapter 14 Preview Section 1 Fluids and Pressure**

Forces in Fluids Preview Section 1 Fluids and Pressure Section 2 Buoyancy and Density Concept Map

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**Chapter 14 Fluids and Pressure**

Section 1 Fluids and Pressure Fluids and Pressure A fluid is a nonsolid state of matter in which the atoms or molecules are free to move past each other. A fluid is any material that can flow and that takes the shape of its container. Liquids and gases are fluids.

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**Fluids and Pressure, continued**

Chapter 14 Section 1 Fluids and Pressure Fluids and Pressure, continued Pressure is the amount of force exerted on a given area. Moving particles of matter create pressure by colliding with one another and with the walls of their container. Fluids exert pressure evenly in all directions.

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**Fluids and Pressure, continued**

Chapter 14 Section 1 Fluids and Pressure Fluids and Pressure, continued Any force, such as the weight of an object, acting on an area creates pressure. The SI unit for pressure is the pascal. One pascal (1 Pa) is the force of one newton exerted over an area of one square meter (1 N/m2).

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**Chapter 14 Atmospheric Pressure**

Section 1 Fluids and Pressure Atmospheric Pressure The atmosphere is the layer of nitrogen, oxygen, and other gases that surrounds Earth. The pressure caused by the weight of the atmosphere is called atmospheric pressure.

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**Atmospheric Pressure, continued**

Chapter 14 Section 1 Fluids and Pressure Atmospheric Pressure, continued The atmosphere extends about 150 km above Earth’s surface. Atmospheric pressure changes as you travel through the atmosphere. At the top of the atmosphere, pressure is almost nonexistent because there are fewer gas particles and they rarely collide.

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Chapter 14 Forces in Fluids Atmospheric Pressure

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**Chapter 14 Water Pressure**

Section 1 Fluids and Pressure Water Pressure Water is a fluid. So, like the atmosphere, water exerts pressure. Water pressure increases as the depth of the water increases. Water pressure depends on depth, not on the total amount of fluid present.

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**Water Pressure, continued**

Chapter 14 Section 1 Fluids and Pressure Water Pressure, continued A person swimming 3 m below the surface of a small pond feels the same pressure as a person swimming 3 m below the surface of a large lake. Because water is about 1,000 times denser than air, water exerts more pressure than air does.

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**Pressure Differences and Fluid Flow**

Chapter 14 Section 1 Fluids and Pressure Pressure Differences and Fluid Flow Fluids flow from areas of high pressure to areas of low pressure. Differences in air pressure help explain the way your body breathes and the way tornadoes create damaging winds.

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Chapter 14 Forces in Fluids

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**Buoyant Force and Fluid Pressure**

Chapter 14 Section 2 Buoyancy and Density Buoyant Force and Fluid Pressure All fluids exert an upward force called buoyant force. Buoyant force is the upward force that keeps an object immersed in or floating on a liquid. Buoyant force is caused by differences in fluid pressure.

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Chapter 14 Forces in Fluids Buoyant Force

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**Buoyant Force and Fluid Pressure, continued**

Chapter 14 Section 2 Buoyancy and Density Buoyant Force and Fluid Pressure, continued A Greek mathematician named Archimedes discovered how to find buoyant force. Archimedes’ principle states that the buoyant force on an object in a fluid is an upward force equal to the weight of the volume of fluid that the object displaces.

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Chapter 14 Forces in Fluids

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**Weight Versus Buoyant Force**

Chapter 14 Section 2 Buoyancy and Density Weight Versus Buoyant Force An object in a fluid will sink if the object’s weight is greater than the buoyant force (the weight of the fluid that the object displaces). An object floats only when the buoyant force on the object is equal to the object’s weight.

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**Buoyant Force on Floating Objects**

Chapter 14 Forces in Fluids Buoyant Force on Floating Objects

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**Chapter 14 Density and Floating Density is mass per unit volume.**

Section 2 Buoyancy and Density Density and Floating Density is mass per unit volume. Any object that is denser than the surrounding fluid will sink. An object that is less dense than the surrounding fluid will float.

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**Chapter 14 Determining Density**

Section 2 Buoyancy and Density Determining Density To determine the density of an object, you need to know the object’s mass and volume. A balance can be used to find the mass of an object. To find the volume of a regular solid, such as a cube, multiply the lengths of the three sides together.

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**Determining Density, continued**

Chapter 14 Section 2 Buoyancy and Density Determining Density, continued To find the volume of an irregular solid, use water displacement. By measuring the volume of water that the object displaces, or pushes aside, you find the volume of the object itself.

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**Changing Overall Density**

Chapter 14 Section 2 Buoyancy and Density Changing Overall Density The overall density of an object can be changed by changing the object’s shape, mass, or volume. Submarines use ballast tanks to change their overall density and dive under water. As water is added to the tanks, the submarine’s mass increases, but its volume stays the same.

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**Changing Overall Density, continued**

Chapter 14 Section 2 Buoyancy and Density Changing Overall Density, continued Most bony fishes have an organ called a swim bladder that allows them to adjust their overall density. An inflated swim bladder increases the fish’s volume, which decreases the fish’s overall density so the fish does not sink.

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Chapter 14 Forces in Fluids

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