Transcript Chapter 13 Lesson 1

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/m2)
1. 101.3 kPa at Sea level
2. 1000 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 m2, how much pressure does the
book exert?
P=F/A
30 N / 0.06 m2
= 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)
Low Pressure
High Pressure
High to Low causes lift for an airplane
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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.
High Pressure
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”
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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
Weight
_________
 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.
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 … sink
< 1 … float
2. Force Analysis
 weight vs. buoyant force
weight > buoyant force
sink
weight < buoyant force
float
weight = buoyant force
suspended
Quiz Review Content
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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.