Chapter 11 Notes Forces in Fluids

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

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

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

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

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

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

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

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

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