Transcript fluid
Chapter 14 Forces in Fluids Preview Section 1 Fluids and Pressure Section 2 Buoyancy and Density Concept Map < Back Next > Preview Main Chapter 14 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. < Back Next > Preview Main 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. < Back Next > Preview Main 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). < Back Next > Preview Main Chapter 14 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. < Back Next > Preview Main 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. < Back Next > Preview Main Chapter 14 Forces in Fluids Atmospheric Pressure < Back Next > Preview Main Chapter 14 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. < Back Next > Preview Main 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. < Back Next > Preview Main 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. < Back Next > Preview Main Chapter 14 Forces in Fluids < Back Next > Preview Main 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. < Back Next > Preview Main Chapter 14 Forces in Fluids Buoyant Force < Back Next > Preview Main 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. < Back Next > Preview Main Chapter 14 Forces in Fluids < Back Next > Preview Main 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. < Back Next > Preview Main Chapter 14 Forces in Fluids Buoyant Force on Floating Objects < Back Next > Preview Main Chapter 14 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. < Back Next > Preview Main Chapter 14 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. < Back Next > Preview Main 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. < Back Next > Preview Main 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. < Back Next > Preview Main 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. < Back Next > Preview Main Chapter 14 Forces in Fluids < Back Next > Preview Main