2. Fluids are substances that can flow. That means liquids and gases can flow so they are fluids.

3. Density  Density is a measure of the “compactness” of a substance  Density is mass per unit of volume  Density formula- D= Mass/Volume  Common Density units include:  g/cm3 and kg/m3  Turns out that 1cm3 (1cc) of water has a mass of 1g and 1 cm3 of water is the same amount as 1ml of water  How convenient!!!

4. Pressure-Force per unit Area  Pressure is a force that is exerted over an area  Pressure formula is: Pressure=Force/area  Standard unit of pressure (SI) is the Pascal, which is newton/m2.  1Pa is about the same amount of pressure that a $1 bill resting on a flat table.  Book Demonstration

5. Pressure in a liquid  Pressure in water is due to the weight of the water directly above you ( include the weight of the atmosphere also)  Pressure DOES NOT depend on the volume of the liquid. ( You would feel the same pressure 3 feet down in the middle of the ocean as you would in a 3 foot deep mini-pool.)  Pressure under water is directly related to the depth. The deeper you go, the greater the pressure  Water seeks it’s own level? Huh?

6. More Pressure in a Liquid  Liquid pressure is exerted equally in all directions.  Go under water and feel the pressure on your body (ears maybe). Then tilt your head. The pressure doesn’t change, showing that the pressure is equal in all directions.

7. Buoyancy in a Liquid  Buoyancy (buoyant force) is the force exerted by water on a submerged object  If the weight of a submerged object is greater than the upward buoyant force, the object sinks.  If the weight and buoyant forces are equal, the object remains at any level.  If the buoyant force is greater than the weight, the object will rise and float.

8. Archimede’s Principle  A completely submerged object will ALWAYS displace a volume of liquid equal to it’s own volume  An immersed object is buoyed up by a force equal to the weight of the fluid it displaces  “immersed” means completely or partially submerged

9. Float or Sink  Why do ice and wood float?  Why does iron sink?  When or how can iron float?  A floating object will displace a weight of fluid equal to it’s own weight?  The buoyant force of a liquid varies with the type of liquid. (a ship will float higher in salt water than in freshwater.) Why?

10. Pressure  What is the main difference between a gas and a liquid?  What would happen to the air pressure inside a bike tire if we double the amount of air in the tire?  What would happen to the density of the air in the tire if we double the amount of air in the tire?  What would happen to the pressure of the air in the tire if we did not change the amount of air, but we squeezed the tire down to ½ of it’s volume?  What would happen to the density of the air if we did not change the amount of air, but we squeezed the tire down to ½ of it’s volume?

11. Boyle’s Law  As long as the temperature does NOT change, Boyle’s Law applies.  The Law is: the product of the pressure and volume of a gas does not change.  P1V1=P2V2  P1 and V1 are the original pressure and volume  P2 and V2 are the 2 nd pressure and volume  http://video.google.com/videoplay?docid=- 914214099352708812# http://video.google.com/videoplay?docid=- 914214099352708812#

12. Weight of the Atmosphere  We live at the bottom of an ocean (of air)!  The weight of the air above us is what causes air pressure.  What causes anything to have weight?  At sea level, standard air pressure is about 15 pounds per square inch.  That figures out to be about 2000 pounds of pressure for the average person.

13. Atmosphere Facts  Air pressure decreases as you to go up in altitude.  http://www.nasa.gov/audience/foreducators/topnav/mat erials/listbytype/What_is_Atmospheric_Pressure.html http://www.nasa.gov/audience/foreducators/topnav/mat erials/listbytype/What_is_Atmospheric_Pressure.html  The air closest to the ground is the most compact, thus has the highest pressure.  Air will always flow from higher to lower pressure until equilibrium is reached.  Examples: balloon, breathing, Metrodome, wind, drinking through a straw

14. Barometer  A barometer measures the atmospheric pressure  As the air gets heavier, it pushes down on the liquid mercury with more force, causing the mercury in the tube to rise.  This is similar to what happens when You drink through a straw.

15. Pascal’s Principle  A change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid  Example: the water pressure throughout a city is equal no matter where you are located.

16. Bernoulli’s Principle  Fast flowing fluids, such as air, will have less pressure than slower moving fluids.

17. More Bernoulli  http://home.earthlink.net/~mmc1919/venturi. html http://home.earthlink.net/~mmc1919/venturi. html  Fast moving air has less pressure than slower moving air.