Chapter 13 Lesson 1 “Pressure”

I. Pressure A. Def – the amount of force exerted over an area. 1. Tires – gases push on the outside walls of tires B. Formula - P = F / A C. Measured in Pascals (N/m 2 ) kPa at Sea level Pa = 1 kPa

D. Our Atmosphere 1. Gas layer that covers the earth. 2. Perfect amount of gases a. Nitrogen – 78% b. Oxygen – 21% c. Carbon Dioxide -.04% d. Water vapor, dust, argon 3. Air pressure ↓’s as altitude increases (Indirect)

E. A book has a force of 30 Newton's while resting on a table. If the area of the book is 0.06 m 2, how much pressure does the book exert? P = F / A 30 N / 0.06 m 2 = 500 Pa Or 0.5 kPa

Chapter 13 Lesson 2 “Forces and Pressures in Fluids”

I. Pascal’s Principle A. Def – a pressure applied to a fluid is transmitted throughout the whole fluid. 1. Squeezing toothpaste 2. Squeezing one end of a balloon B. Hydraulic Machine – uses oil like liquid to multiply input force up to 10x.

II. Bernoulli’s Principle A. Def – as the velocity of a fluid increases, the pressure of the fluid decreases. 1. Ex: blowing 2 pop cans.

2. Airplanes (pg. 213) High Pressure Low Pressure High to Low causes lift for an airplane

As the airplane speeds down the runway, air rushes over and under the wings. The air, going over the wings, goes faster and faster, there is less and less pressure above the wings. Soon there is much more pressure below the wings than above. This pressure pushes up on the wings and the airplane is lifted into the sky.

DEMO -Fill a beaker or cup full of water to the brim. -Add one drop of food coloring -Insert a straw to the middle of the beaker vertically. -Blow across the top of the straw. Notice the water inside of the straw. -What happens and why?

3. Venturi Effect a. Def – reduced air pressure outside of skyscrapers has caused windows to be blown out.

Low Pressure High Pressure

13.2 Assignment: Write a paragraph for why a “curve ball” in baseball demonstrates the Bernoulli Principle.

Chapter 13 Lesson 3 “Buoyancy”

What Archimedes realized about buoyancy Archimedes solved many problems for King Heiro of Syracuse. His most famous solution is associated with Heiro's new crown. Heiro had given the goldsmith the exact amount of gold needed for the crown. After it was made, Heiro suspected that it might not have as much gold as it was supposed to. King Heiro summoned Archimedes, and Archimedes was bewildered with the king's problem. But later, when Archimedes got into his full bathtub, it occurred to him that the volume of water that spilled out of the tub was equal to the volume he displaced. Reasoning that a much lower volume of water would be displaced by something denser (like gold) even though of equal weight, he saw the answer to the king's problem. The next day Archimedes told they king of his discovery. Archimedes put the king's new crown in a tub of water and found that the crown indeed displaced more water than the same weight of gold (it occupied more volume because it had been adulterated with lower density silver). The goldsmith was immediately beheaded.

I. Buoyancy A. Def – the ability of a fluid to exert an upward force on an object placed in it. 1. results in an apparent loss of _________  easy to lift  opposite of gravity B. History 1. Archimedes's Principle  the buoyant force on an object is equal to the weight of fluid displaced by the object. Weight

In other words…think of the clay activity we did earlier in this chapter.

C. Two Ways to tell if an object can float 1. Density > 1 … < 1 … 2. Force Analysis  weight vs. buoyant force weight > buoyant force weight < buoyant force sink float sink float

weight = buoyant force suspended

Quiz Review Content Know Pascal’s Principle and what it applies to. Know the pressure equation and units What is the definition of a fluid? What is the relationship between altitude and pressure? Know Bernoulli’s Principle and what it applies to. Know what the Venturi Effect is. Be able to calculate force, area, and pressure. SHOW YOUR WORK!!!!! There is also an extra credit question on the quiz, but you will have to get it right to get the extra credit.