What is a Fluid? A substance that has the capacity to flow and assume the form of the container.

Examples? All gases and liquids!

Fluids and the Particle Model Water- particles held close together - poured in glass, particles slide over each other - take form of glass Air- particles further apart - move in every direction to fill space of the container

Fluid or not? Smoke → Fluid (and colloid) 2. Toothpaste→ Fluid Hair Gel → Sand in Hourglass → Not a Fluid (doesn’t flow, forms pile)

Types of Fluids Compressible Fluids - fluid whose volume change Ex. air - gases are compressible fluids

Incompressible Fluids - a fluid whose volume cannot be varied. Ex. blood - Liquids are incompressible fluids

What is Pressure? Pressure is the result of a force applied in a perpendicular fashion to a surface.

Force: -Force is an action that modifies the movement of an object or the shape of an object to change. ex. Key when texting, Playing with play dough - produced by action, or attraction between objects. ex. Sun and moon

Pressure & Particles Pressure is the force exerted by particles when they collide with a constricting surface

Effect of Force on Pressure If the force is varied, and the area is kept constant 1. If the force increases, then pressure increases. 2. If the force decreases, then pressure decreases.

Blocks on table As more blocks are added the force increases, but the area stays the same.

Effect of Surface Area If the Surface Area is varied, and the Force is kept constant 1. If the surface area increases, pressure decreases. 2. If the surface area decreases, pressure increases.

Which footwear would you use in deep snow? Black snow boots Snowshoes

Boots: less surface area, more pressure →SINKING IN SNOW! Snowshoes: More surface area, less pressure →YOU DON’T SINK

Mathematical Equation P = F A P: Pressure in N/m2 F: Force in N (newton) A: Surface Area in m2

Pressure measured in units called: Pascals(Pa), 1 Pa=1 N/m2 (very small) 1 kPa=1000 Pa= 1000 N/m2 Atmospheric Pressure=Air Pressure (at sea level) 101.3 kPa=760 mm hg= 1 atm

Ex. 1 What is the pressure exert? F= 1000 N 10 m 10 M A= l x w A= 10 m x 10 m A= 100 m2 P = F/A= 1000N/ 100 m2 P = 10 N/m2 P= 10 Pa

Ex. 2 What is the force applied below? P = 20 Pa A= l x W= 15m x 10m A= 150 m2 P = F A 20 Pa = F 150 m2 F = 3000 N 10 m 15 m

Ex. 3 : What is the pressure in kPa exerted when 100 N of force is applied to a cylinder with a radius of 10 cm? r=10 cm = 0.1 m A= ∏r2 A= (3.14)(0.1 m)2 A= 0.0314 m2

P = F A P= 100 N 0.0314 m2 P = 3185 Pa P = 3185 Pa ÷ 1000 = 3.19 kPa

Incompressible Fluid The FORCE exerted comes from the mass of the fluid that is situated ABOVE the object If more fluid above, greater force exerted by fluid, more pressure.

Density and Pressure The more dense the fluid , the greater the pressure, and the less dense, the lower the pressure. ex. Sea water d=1.03 g/cm3 Distilled Water d= 1.00 g/cm3

Compressible Fluid The number of collisions involving fluid particles and other fluid particles or objects

Factors that Affect Pressure # of particles, more particles, more pressure Temperature- temp.,faster particles more collisions

Pressure and Volume (Boyle’s Law)

Pressure If pressure , then volume Ex. Weather balloon rises, volume , pressure as altitude (balloon pops!)

The Ear External Pressure , the eardrum swells Discomfort disappears when pressure becomes normal

Low pressure High Pressure

General technical principles A fluid naturally moves from a zone of high pressure toward a zone of low pressure

Second Principle Pressure applied to the surface of a fluid inside a closed container gets uniformly distributed to every part of the fluid (Pascal’s principle) Ex. Car brakes

Third Principle A transfer of pressure in a fluid can increase the force involved. Ex. Hydraulic Car Lift

Natural Mechanisms Heart works like a ________: - _______________causes blood to circulate - ___________Pressure (maximum pressure, heart beating) (minimum pressure, heart resting)

Sphygmomanometer(mm Hg) (normal 120/75 Hg, 16/10 kPa)

2. Inhalation and Exhalation -Differences in pressure between the chest cavity and outside

3.Bike pump As the plunger goes down air is compressed into an increasingly smaller volume. As volume decreases, the pressure increases. When the pressure is higher in the pump than the tire, then the air moves from the pump to the tire