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

2. Agenda9/23/08 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/m 2 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 Pressure 1 = Pressure 2

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