Chapter 11 Notes

1. Chapter 11 Notes Forces in Fluids

2. Section 1 - Pressure • Pressure decreases as the area over which a force is distributed increases. • increase surface area, decrease pressure • ice skates • Pressure - equal to the force exerted on a surface divided by the total area over which the force is exerted. • Pressure = force/area • pressure units = pascal • 1 Pa = 1N/m2 Chapter 11

3. Pressure cont’d • fluid - substance which can easily flow • All of the forces exerted by the individual particles in a fluid combine to make up the pressure exerted by the fluid. • Balanced pressure - air pressure • as elevation increases, air pressure decreases • water pressure increases as depth increases Chapter 11

4. Section 2 - Floating and Sinking • Buoyant force - acts in an upward direction, against the force of gravity. • Makes an object feel lighter • Archimedes’ principle - the buoyant force on an object is equal to the weight of the fluid displaced by the object • floating and sinking - pg. 383 Chapter 11

5. Floating & Sinking cont’d. • density = mass/volume units g/mL or g/cm3 • water density = 1 g/mL pg.363 • By comparing densities, you can predict whether an object will float or sink in a fluid. Chapter 11

6. Section 3 – Pascal’s Principle • Pascal’s principle - When force is applied to a confined fluid, an increase in pressure is transmitted equally to all parts of the fluid. • Page 390 - Demonstration Chapter 11

7. Hydraulic System • Multiplies a force by applying the force to a small surface area. The increase in pressure is then transmitted to another part of the confined fluid, which pushes on a larger surface area. • Small force over small area results in a larger force exerted by a larger area at another place. • Car brakes, repair shop lift, fire truck ladder Chapter 11

8. Section 4 - Bernoulli’s Principle • Wright brothers • Fluid naturally flows from an area of hogh pressure to an area of low pressure. Chapter 11

9. Bernoulli’s principle • As the speed of a moving fluid increases, the pressure within the fluid decreases. • Air moves at different speeds above and below objects. • Difference in pressure causes lift or downward force • wings pg. 395 Chapter 11

10. Chapter 11 - Vocabulary List • Pressure • Pascal’s principle • hydraulic system • buoyant force • Archimedes’ principle • Bernoulli’s principle Chapter 11

11. Bernoulli’s Principle cont’d. • Bernoulli’s principle helps explain how planes fly. It also helps explain why smoke rises up a chimney, how an atomizer works, and how a flying disk glides through the air. Chapter 11