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Chapter 16

Chapter 16 . Lesson 2. Properties of Fluids. A fluid is a gas or a liquid despite their weight ships are able to float. greater force pushing up on the ship opposes the weight—or force—of the ship pushing down. Archimedes’ Principle. Buoyant Force

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Chapter 16

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  1. Chapter 16 Lesson 2

  2. Properties of Fluids • A fluid is a gas or a liquid • despite their weight ships are able to float. • greater force pushing up on the ship opposes the weight—or force—of the ship pushing down.

  3. Archimedes’ Principle • Buoyant Force • upward force exerted by a fluid on an immersed object • buoyant force > weight balloon rises • buoyant force < weight balloon sinks • buoyant force = weight balloon floats

  4. Very little water needs to be displaced in order to cancel weight  ball floats on surface. More water needs to be displaced in order to cancel weight  ball floats lower in the water. Not enough water is displaced in order to cancel weight  ball sinks. Archimedes’ Principle • Archimedes’ Principle • the buoyant force on an object in a fluid is equal to the weight of fluid displaced by the object View Buoyancy JAVA Applet. View animations produced by students at Poly Prep Country Day School in Brooklyn, New York.

  5. Density • object will float if its density is less than the fluid it is in. • Suppose you form a steel block into the shape of a hull filled with air. Now the same mass takes up a larger volume. The overall density of the steel boat and air is less than the density of water. The boat will now float.

  6. Pascal’s Principle • Pressure is force exerted per unit area • Blaise Pascal (1692-1662), • a French scientist, discovered a useful property of fluids. • Pascal’s principle • pressure applied to a fluid is transmitted throughout the fluid. • Ex: toothpaste, hydraulic lifts

  7. Pascal’s Principle • Pascal’s Principle • pressure applied to a fluid is transmitted unchanged throughout the fluid View hydraulics explanation.

  8. Applying the Principle • pipe filled with fluid connects small and large cylinders. • pressure applied to the small cylinder is transferred through the fluid to the large cylinder

  9. Applying the Principle • pressure remains constant throughout the fluid • more force is available to lift a heavy load by increasing the surface area.

  10. WORK: 1000 N = F2 250 m2 10 m2 Pascal’s Principle • A car weighing 1000 N sits on a 250 m2 platform. What force is needed on the 10 m2 plunger to keep the car from sinking? GIVEN: Platform: F = 1000 N A = 250 m2 Plunger: F = ? A = 10 m2 (1000N)(10m2)=(250m2)F2 F2= 40 N

  11. WORK: 1000 N = F2 5 m2 2 m2 Pascal’s Principle • A disgruntled cow that weighs 1000 N sits on a 5 m² piston. What force would need to be applied to a 2 m² piston? GIVEN: Platform: F = 1000 N A = 5 m2 Plunger: F = ? A = 2 m2 (1000N)(2m2)=(5m2)F2 F2= 400 N

  12. Bernoulli’s Principle • Bernoulli’s Principle • as the velocity of a fluid increases, the pressure exerted by the fluid decreases • EX:airplane lift, curve balls Bernoulli – why planes fly

  13. Bernoulli’s Principle • demonstrate Bernoulli’s principle • blow across the top surface of a sheet of paper. • The paper will rise. • velocity of the air over the top is greater than that of the quiet air below it. • Net force below raises the paper

  14. Bernoulli’s Principle Airplane lift The downward force decrease and the lifting force increases. Bernoulli’s principle states that as the velocity of a fluid increases the pressure exerted by the fluid decreases. View airplane wings explanation.

  15. Bernoulli’s Principle Venturi Effect - Atomizers View atomizer explanation.

  16. Bernoulli’s Principle • Venturi Effect • fluids flow faster through narrow spaces causing reduced pressure • EX: garden sprayer, atomizer

  17. Bernoulli’s Principle • This allows the water in the hose to flow at a high rate of speed, creating a low pressure area above the strawlike tube. • The concentrated chemical solution is sucked up through the straw and into the stream of water. • The concentrated solution is mixed with water, reducing the concentration to the appropriate level and creating a spray that is easy to apply.

  18. Fluid Flow • Another property exhibited by fluid is its tendency to flow. The resistance to flow by a fluid is called viscosity. • When a container of liquid is tilted to allow flow to begin, the flowing particles will transfer energy to the particles that are stationary. • Temperature and viscosity are inversely related; that is higher temperature means lower viscosity

  19. Fluid Flow • In effect, the flowing particles are pulling the other particles, causing them to flow, too. • If the flowing particles do not effectively pull the other particles into motion, then the liquid has a high viscosity, or a high resistance to flow. • If the flowing particles pull the other particles into motion easily, then the liquid has low viscosity, or a low resistance to flow.

  20. Temperature and viscosity are inversely related; that is higher temperature means lower viscosity

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