Unit 23 - Fluid Pressure

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Properties of Fluids

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Unit 23 - Fluid Pressure

  1. 1. Forces in Fluids<br />Chapter 23 <br />
  2. 2. Thought Questions<br />Why is the electricity produced at the bottom of dams?<br />When you catch a deep-sea fish, why does its eyes pop-out?<br />Why do your ears pop on an airplane or up in the mountains?<br />
  3. 3. Pressure<br />                                                                            <br />Pressure is equal to the force applied to a surface, divided by the area.<br />
  4. 4. Equations for Pressure<br />Pressure = Force/surface area<br /><ul><li>Pressure = Newtons (Kg x m/s2)</li></ul>side x side<br /><ul><li>Units are in Pascals or N/m²</li></li></ul><li>Fluids<br />A substance that can easily change its shape, such as liquids and gases.<br /><ul><li>The molecules in a fluid have a certain amount of force (mass and acceleration) and exert pressure on surfaces they touch.</li></li></ul><li>
  5. 5. FLUID PRESSURE<br /><ul><li>All the molecules add up together to make up the force exerted by the fluid.</li></li></ul><li>High<br />Microburst - High Pressure Air<br />High Pressure<br />
  6. 6. Low Pressure<br />L<br />Rising Air<br />Suction<br />L<br />
  7. 7. <ul><li>Air has a mass of 1Kg/m³</li></ul>AIR PRESSURE<br /><ul><li>Gravity creates an air pressure of 10.13N/m³ at sea level.</li></li></ul><li>Pressure and Elevation<br /><ul><li>Air Pressure decreases as elevation increases.</li></ul>Climbers above 20,000 feet need oxygen because the air is so thin<br />
  8. 8. Pressure and Elevation<br /><ul><li>Air Pressure decreases as elevation increases.
  9. 9. Astronomical telescopes are placed on mountain tops because the thinner air means less interference with the stars</li></ul>Mauna Kea at 13,700 feet<br />Is above 40% of the atmosphere<br />
  10. 10. Extreme Elevations<br />Commercial flights fly higher than you can breathe. So, they must pressurize the cabin<br />Mount Everest at 29,600 feet<br />Is above 70% of the atmosphere<br />35,000 feet<br />
  11. 11. Extreme Elevations<br />Astronauts have no actually left the atmosphere. The microscopically thin atmosphere results in drag on spacecraft and satellites.<br />Nonetheless, it is far too thin to breathe and cold to survive without spacesuits<br />100 km<br />
  12. 12. Highest Pressure<br />Very Low pressure<br />Higher Pressure<br />The whole system is a low pressure, but it is extremely low in the eye.<br />
  13. 13. Highest Pressure<br />Very Low pressure<br />Higher Pressure<br />Pressure always flows from high to low, which creates the high velocity winds toward the eye.<br />
  14. 14. Storm Surge<br />Very Low pressure<br />Higher Pressure<br />The Low Pressure creates a vacuum that pulls water up into a dome. The high winds push this dome on shore.<br />
  15. 15. Storm surges are the leading cause of damage<br />Very Low pressure<br />Higher Pressure<br />The force of the air moving toward the eye causes extreme winds in excess of 100 mph.<br />
  16. 16. Pressure and Depth<br /><ul><li>Water pressure increases with depth.</li></li></ul><li>Water Pressure<br />Marianas Trench = 10,911 m (35,800 ft) or 1,100 atmospheres.<br />That is the equivalent of an average-sized person holding up 48 jumbo jets or 400 times the pressure in automobile tires.<br />
  17. 17.
  18. 18. Pascal&apos;s Principle<br /><ul><li> When a force is applied to a confined fluid, the increase in pressure is transmitted equally to all parts of the fluid.
  19. 19. These styroform cups were crushed outside of submarines.</li></li></ul><li>Transmitting Pressure in a Fluid<br />When force is applied to a confined fluid, the change in pressure is transmitted equally to all parts of the fluid.<br />
  20. 20. Hydraulic Devices<br />In a hydraulic device, a force applied to one piston increases the fluid pressure equally throughout the fluid.<br />
  21. 21. Hydraulic Devices<br />By changing the size of the pistons, the force can be multiplied.<br />
  22. 22. Hydraulic Brakes<br />The hydraulic brake system of a car multiplies the force exerted on the brake pedal.<br />
  23. 23. Buoyancy<br />The tendency or ability of an object to float.<br />
  24. 24. Buoyancy<br />The pressure on the bottom of a submerged object is greater than the pressure on the top. The result is a net force in the upward direction.<br />
  25. 25. Buoyant Force<br />The upward force exerted by a fluid on a submerged or floating object.<br />
  26. 26. Buoyancy<br />The buoyant force works opposite the weight of an object.<br />
  27. 27. Archimedes’ principle:<br />Buoyant Force on an object immersed in a liquid equals the weight of the liquid displaced.<br />
  28. 28. Density and buoyancy: An object that has a greater density than the fluid it is in, will sink. If its density is less than the fluid it will float.<br />Density<br />
  29. 29. It does not matter that Mercury is a liquid. It is so dense, most things float on it<br />
  30. 30. Buoyancy of gases in liquids <br />Buoyancy of gases in gases<br />Gases have less density than water, so they rise up to the surface<br />Some gases, like Helium, are lighter than air and rise.<br />Some gases, like carbon dioxide, are heavier than air and sink.<br />
  31. 31. How do super heavy container ships float?<br />
  32. 32. A solid block of steel sinks in water. <br />A steel ship with the same mass floats on the surface.<br />
  33. 33. A solid block of steel sinks in water. A steel ship with the same mass floats on the surface.<br />Air<br />steel<br />
  34. 34. Take the mass of the displaced area (steel and air) and compare it to the mass of the water of that volume.<br />If the displaced area weighs less it will float.<br />Water<br />
  35. 35. Density<br />Changes in density cause a submarine to dive, rise, or float.<br />
  36. 36. Density<br />Changes in density cause a submarine to dive, rise, or float.<br />
  37. 37. Density<br />Changes in density cause a submarine to dive, rise, or float.<br />
  38. 38. Density<br />Gases can actually be made from solids using chemical reactions to create additional buoyancy.<br />
  39. 39. DENSITY OF WATER<br />1g/cm³<br />or 1 g/ml<br />

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