DAILY QUESTION September 23, 2008

1. DAILY QUESTION September 23, 2008 • What is a buoyant force?

2. Agenda 9/23/08 • Daily Question • Check-in Ch 3 Sect 1 Wksht • Chapter 3 Section 2 Notes • Chapter 3 Section 2 Review Wksht Assignments: 1.Ch 3 Section 2 Review Wksht due 9/24

3. Fluids (page 80) • Do Not have a fixed shape • Gases and Liquids • Particle are able to move past each other

4. Buoyant Force (page 80) Upward force exerted on an object by a fluid • Examples: Ships and rubber ducks float because less dense than water and the buoyant force pushes against them to keep them afloat • Result of pressure • The amount of force exerted on a given area • ↑Depth = ↑Pressure • Buoyant Force is greater than downward force, so the object floats. (ice on water)

5. Buoyant Force

6. Archimedes’ principle (page 81) • 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 • When the object is completely submerged, the volume of the displaced water equals the volume of the object

7. Archimedes’ principle Volume of the displaced water = volume of the object

8. Steel Ships Float ?!? • Steel is 8 times denser than water • However, ships have a hollow shape making the density of the boat less than water.

9. Pressure (page 83) Pressure = force/area • SI Unit for pressure is pascal (Pa) • 1 Pa = 1 Newton/m2 • Fluids exert pressure equal in all directions • Example: Blowing bubbles…. Bubbles are round

10. Pascal’s principle (page 84) • A fluid in equilibrium contained in a vessel exerts a pressure of equal intensity in all directions • Pressure1 = Pressure2

11. Hydraulic Devices (page 85) Use liquids to transmit pressure from one point to another • Can multiply force

12. Fluids in Motion (page 85-86) Viscosity – liquid’s resistance to flow Examples: Honey, Molasses Bernoulli’s Principle – fluid pressure decreases as the speed of a moving fluid increases ↑ Fluid Speed = ↓ Fluid Pressure