FORCES in FLUIDS
Chapter 7
Mr. Swope
Unit essential question
How do fluids exert force?
Lesson One Essential
Questions
• How do fluids
exert pressure?
• How does
atmospheric
pressure varies
with depth?
• How does depth
and density affect
water pressure?
•
What are
examples of fluids
flowing from high
to low pressure?
Lesson 1 Fluids and Pressure
Lesson 2 Buoyant Force
Lesson 3 Fluids and Motion
Lesson one
Fluids Exert Pressure
•
A
_________ is any material that can flow and that takes the
_______
________
shape of its container. Fluids include
and
.
All fluids exert pressure, which is the amount of force exerted per unit area of a
surface.
The
______________ in fluids are constantly ___________.
________________ with each other and the walls of the
container they are in. These collisions create force called
Calculating pressure
•
________________
___________.
Pressure can be calculated by using
the following equation:
Lesson one terms
Fluid
Pressure
Calculating Pressure
Paschal
Atmospheric pressure
•
The SI unit for pressure is the
_________. One pascal (1 Pa) is
____________
the force of one
exerted over an area of one
square meter (1 N/m2).
Pressure, Force, and Area
•
Pressure and Bubbles Soap bubbles get rounder as they get bigger
because fluids exert pressure ____________________ in all directions.
•
Since air is a fluid, adding air to an air bubble causes it to expand in all
directions at once. This makes a
Atmospheric Pressure
_____________.
_________________
•
The
is the thin layer of nitrogen,
oxygen, and other gases that surrounds Earth.
•
____________________ is the pressure caused by the
weight of the atmosphere. Gravity pulls down on the gases toward Earth.
_____________________ is exerted on everything on Earth,
including you.
The air inside this balloon exerts pressure that keeps the balloon inflated against
atmospheric pressure.
•
Variation of Atmospheric Pressure The atmosphere stretches about
150 km above the Earth’s surface, but about 80% of the atmosphere’s
Page 1
FORCES in FLUIDS
Chapter 7
Mr. Swope
gases are found within 10 km. At the top of the atmosphere, pressure is
almost nonexistent.
_______________
With a classmate Analyze
how atmospheric pressure
varies with depth.
Atmospheric Pressure and
As you travel
through the atmosphere, atmospheric pressure changes. The further down
through the atmosphere you go, the greater the pressure is.
At sea level, atmospheric pressure is _____________________.
At the top of Mount Everest, atmospheric pressure is about _________________
At the top most of our atmosphere, the pressure is almost ______________.
Pressure Changes and Your Body If you travel to higher or lower points in the
atmosphere, the fluids in your body have to adjust to maintain
pressure.
Pressure changes in your body
equal
____________________
Explain how depth and
density affect water
pressure.
•
Water is a fluid. So, it exerts pressure like the atmosphere does.
•
Water Pressure and
water pressure depends on depth.
___________
Like atmospheric pressure,
_____________
Makes a Difference Because water is more dense
than air, a certain volume of water has more ___________—and weighs more—
than the same volume of air. Water exerts ____________________ than air.
Water Pressure
_____________.
As you go deeper in the water, water pressure is
Water pressure changes as you go to the bottom of a deep pool.
_____________
Water is about 1000 times more ______ than air.
is
the amount of matter in a given volume, or mass per unit volume. So, water
exerts more pressure than air.
PRESSURE DIFFERENCES AND FLUID FLOW
Fluids flow from areas of _________ pressure to areas of low _______________.
High pressure
Low-pressure
Why does liquid flow up a straw when you're drinking a fluid?
Pressure Differences and Fluid Flow
•
Just by drinking through a straw you can observe an important property
of fluids: Fluids flow from areas of high pressure to areas of __________
pressure.
•
Pressure Difference and Breathing The next slide shows how exhaling
causes fluids to flow from high to low pressure.
Give examples of fluids
flowing from high to low
Page 2
____________________
Pressure differences in
When you inhale, muscles increase the space in your chest and gives your lungs
FORCES in FLUIDS
Chapter 7
Mr. Swope
pressure.
•
•
•
•
Describe how
fluids exert
pressure.
Analyze how
atmospheric
pressure varies
with depth.
Explain how
depth and density
affect water
pressure.
Give examples of
fluids flowing
from high to low
pressure.
Lesson Two Essential
Questions
• What is the
relationship
between fluid
pressure and
buoyant force.
•
What determines
whether an object
will float or sink in
a fluid.
•
What is the role
of density in an
object’s ability to
float.
•
How can the
overall density of
an object can be
changed.
Lesson Two Terms
Buoyant force
Archimedes Principle
room to expand. The pressure in your lungs becomes lower than the air pressure
outside your lungs. Air then flows into your lungs, from high pressure to lowpressure.
•
_______
air pressure inside a tornado is very
. Because the air
pressure outside of the tornado is higher than the pressure inside,
_____________________ into the tornado.
•
The rushing air causes the tornado to be like a giant vacuum cleaner.
Lesson one evaluation
End of lesson one
Lesson two
Buoyant Force
Buoyant force
•
____________________ is the upward force that
keeps an object immersed in or floating on a liquid.
____________________
Water exerts
on all sides of an
object. The pressure exerted horizontally on one side of the object is equal to the
pressure each exerted on the opposite sides.
Buoyant Force and Fluid Pressure,
• There is more pressure at the bottom of an object because pressure
increases with depth. This results in an upward
____________
________ on the object.
_______________
•
Determining Buoyant Force
principle
states that the buoyant force on an object is an upward force equal to
the weight of the fluid that the object takes the place of, or displaces.
Weight versus buoyant force
_____________
•
An object in a fluid will sink if its weight is
greater than the buoyant force.
•
_______________
•
Page 3
_____________________ and Tornadoes The
An object will float only when the
buoyant force on the object is equal to the object’s weight.
FORCES in FLUIDS
Chapter 7
Mr. Swope
____________ Up When ________________________ on an
Explain the relationship
between fluid pressure
and buoyant force.
Predict whether an object
will float or sink in a fluid.
Analyze the role of
density in an object’s
ability to float.
object is greater than the object’s weight, the object is buoyed up (pushed up) in
water.
Will an object sink or float? That depends on the whether the ____________
force is less ____________ or equal to the object’s weight.
Sinking
A rock that weighs 75 N, but _______________ 15 N of water will sink.
Floating
A duck may weigh 9 N and ________________ 9 N of water, so the duck will
float.
Buoying up
When the ___________________ force on an object is greater than the objects
weight, the object is _________________ up or pushed up in the water.
Sinking, Sinking, and Density
_______________ dense than air will sink and air.
_______________________ than air will float in air.
Objects
Finding Density
Explain three methods
that the overall density of
an object can be changed.
________________________________
•
Changing _____________________ The secret of how a ship floats is in
the shape of the ship. Ships made of steel float because their overall
density is less than the density of water.
_____________, which is
Explain the relationship
between fluid pressure
and buoyant force.
Predict whether an object
will float or sink in a fluid.
Analyze the role of
density in an object’s
ability to float.
Explain how the overall
density of an object can
be changed.
This demonstrates how a ship made out of
almost 8 times denser than water, is able to float in water.
Lesson three essential
question
What is the relationship
between pressure and
fluid speed?
___________________________
Page 4
•
•
•
____________________
A submarine is a special
kind of ship that can travel both on the surface of the water and
underwater.
Submarines have ballast tanks that can be opened to allow sea water to
flow in.
_____________
As
is added, the submarine’s mass
increases, but its volume stays the same.
Compressed air is used to blow the water out of the tanks so the submarine can
rise.
•
Changing Volume Like a submarine, some fish adjust their overall
density to stay at a certain depth in the water.
Most bony fishes have an organ called a swim bladder which helps them change
FORCES in FLUIDS
Chapter 7
Mr. Swope
What is the role of lift,
thrust, and wing size inflight?
What is a description of
drag, and how does it
affect lift?
What is Pascal's principle?
Lesson Three Terms
Bernoulli’s principle
Lift
Thrust
Drag
Pascal’s principle
Describe to a classmate
drag, and explain how it
affects lift.
Lesson three evaluation
Describe the relationship
between pressure and
fluid speed.
Analyze the roles of lift,
thrust, and wing size in
flight.
Explain Pascal’s principle.
Describe drag, and explain
how it affects lift.
volume.
End of lesson two
Lesson Three
Fluids and Motion
Fluid Speed and Pressure
Bernoulli’s principle states that as the speed of a moving fluid increases, the
fluid’s pressure decreases.
Describe to a classmate the relationship between pressure and fluid speed.
Factors That Affect Flight
•
_____________________________
Thrust is the forward force produced by a plane’s engine. Lift is the
upward force on the wing as it moves through the air.
•
_________________ wings
Wing Size, Speed, and Lift
keep a plane’s weight low, which also helps it move faster.
__________________ and Birds A small bird must flap its
small wings at a fast pace to stay in the air, but a large bird flaps less.
Analyze with a classmate the roles of lift, thrust, and wing size in flight.
___________________ and Baseball The next slide shows
how a baseball pitcher can take advantage of Bernoulli’s principle to throw a
curveball.
_________________ and Motion in Fluids
•
________________ is the force that opposes or
•
•
restricts motion in a fluid. It is a force that is parallel to the velocity of
the flow.
Drag is usually caused by an irregular flow of air, known as turbulence.
______________________
Lift is often reduced
when turbulence causes drag.
__________________ Principle
•
________________
What Is
Principle? Pascal’s
principle states that a change in pressure at any point in an enclosed
fluid will be transmitted equally to all parts of that fluid.
Pascal’s Principle and Motion Hydraulic devices use
Page 5
FORCES in FLUIDS
Chapter 7
Mr. Swope
_________________ principle to move or lift objects. Liquids
are used in hydraulic devices because liquids cannot be easily compressed into a
smaller space.
Because of Pascal’s principle, the touch of a foot can stop tons of moving metal.
.
End Of Lesson Three
End of Chapter 7
Page 6
FORCES in FLUIDS
Chapter 7
Mr. Swope
Unit essential question
How do fluids exert force?
Lesson One Essential
Questions
• How do fluids
exert pressure?
• How does
atmospheric
pressure varies
with depth?
• How does depth
and density affect
water pressure?
•
What are
examples of fluids
flowing from high
to low pressure?
Lesson 1 Fluids and Pressure
Lesson 2 Buoyant Force
Lesson 3 Fluids and Motion
Lesson one
Fluids Exert Pressure
•
A
fluid is any material that can flow and that takes the shape of its
liquids
gases
container. Fluids include
and
.
All fluids exert pressure, which is the amount of force exerted per unit area of a
surface.
The
tiny particles in fluids are constantly moving.
The particles collide with each other and the walls of the
container they are in. These collisions create force called
Calculating pressure
•
Calculating Pressure
pressure.
Pressure can be calculated by using
the following equation:
Lesson one terms
Fluid
Pressure
Calculating Pressure
Paschal
Atmospheric pressure
•
The SI unit for pressure is the
pascal. One pascal (1 Pa) is the force
newton
of one
exerted over an area of one square meter (1 N/m2).
Pressure, Force, and Area
•
Pressure and Bubbles Soap bubbles get rounder as they get bigger
because fluids exert pressure evenly in all directions.
•
Since air is a fluid, adding air to an air bubble causes it to expand in all
directions at once. This makes a
Atmospheric Pressure
sphere.
atmosphere
•
The
is the thin layer of nitrogen, oxygen, and other
gases that surrounds Earth.
•
Atmospheric pressure is the pressure caused by the weight of
the atmosphere. Gravity pulls down on the gases toward Earth.
Atmospheric pressure is exerted on everything on Earth, including
you.
The air inside this balloon exerts pressure that keeps the balloon inflated against
atmospheric pressure.
•
Variation of Atmospheric Pressure The atmosphere stretches about
150 km above the Earth’s surface, but about 80% of the atmosphere’s
gases are found within 10 km. At the top of the atmosphere, pressure is
almost nonexistent.
Page 7
FORCES in FLUIDS
Chapter 7
Mr. Swope
Depth
Atmospheric Pressure and
As you travel through the atmosphere,
atmospheric pressure changes. The further down through the atmosphere you
go, the greater the pressure is.
At sea level, atmospheric pressure is 101 kPa.
At the top of Mount Everest, atmospheric pressure is about 33 kPa.
At the top most of our atmosphere, the pressure is almost nonexistent.
With a classmate Analyze how atmospheric pressure varies with depth.
Pressure Changes and Your Body If you travel to higher or lower points in the
atmosphere, the fluids in your body have to adjust to maintain equal pressure.
Pressure changes in your body
Water Pressure
Explain how depth and
density affect water
pressure.
•
Water is a fluid. So, it exerts pressure like the atmosphere does.
•
Water Pressure and
pressure depends on depth.
Depth
Like atmospheric pressure, water
Density Makes a Difference Because water is more dense than air, a
certain volume of water has more mass—and weighs more—than the same
volume of air. Water exerts more pressure than air.
Water Pressure
greater
As you go deeper in the water, water pressure is
.
Water pressure changes as you go to the bottom of a deep pool.
Density
Water is about 1000 times more dense than air.
is the amount of
matter in a given volume, or mass per unit volume. So, water exerts more
pressure than air.
PRESSURE DIFFERENCES AND FLUID FLOW
Fluids flow from areas of high pressure to areas of low pressure.
High pressure
Low-pressure
Why does liquid flow up a straw when you're drinking a fluid?
Pressure Differences and Fluid Flow
•
Just by drinking through a straw you can observe an important property
of fluids: Fluids flow from areas of high pressure to areas of low
pressure.
•
Pressure Difference and Breathing The next slide shows how exhaling
causes fluids to flow from high to low pressure.
breathing
Give examples of fluids
flowing from high to low
pressure.
•
Describe how
Page 8
Pressure differences in
When you inhale, muscles increase the space in your chest and gives your lungs
room to expand. The pressure in your lungs becomes lower than the air pressure
outside your lungs. Air then flows into your lungs, from high pressure to lowpressure.
FORCES in FLUIDS
Chapter 7
Mr. Swope
•
•
•
fluids exert
pressure.
Analyze how
atmospheric
pressure varies
with depth.
Explain how
depth and density
affect water
pressure.
Give examples of
fluids flowing
from high to low
pressure.
Lesson Two Essential
Questions
• What is the
relationship
between fluid
pressure and
buoyant force.
•
What determines
whether an object
will float or sink in
a fluid.
•
What is the role
of density in an
object’s ability to
float.
•
How can the
overall density of
an object can be
changed.
Lesson Two Terms
Buoyant force
Archimedes Principle
•
Pressure Differences and Tornadoes The air
pressure inside a tornado is very
low. Because the air pressure
outside of the tornado is higher than the pressure inside,
air
rushes into the tornado.
•
The rushing air causes the tornado to be like a giant vacuum cleaner.
Lesson one evaluation
End of lesson one
Lesson two
Buoyant Force
Buoyant force
•
Buoyant force is the upward force that keeps an object
immersed in or floating on a liquid.
fluid pressure
Water exerts
on all sides of an object. The pressure
exerted horizontally on one side of the object is equal to the pressure each
exerted on the opposite sides.
Buoyant Force and Fluid Pressure,
• There is more pressure at the bottom of an object because pressure
increases with depth. This results in an upward
on the object.
buoyant force
Archimedes’
•
Determining Buoyant Force
principle states
that the buoyant force on an object is an upward force equal to the
weight of the fluid that the object takes the place of, or displaces.
Weight versus buoyant force
Sinking
•
An object in a fluid will sink if its weight is greater than the
buoyant force.
•
Floating
An object will float only when the buoyant force on the
object is equal to the object’s weight.
•
Explain the relationship
Page 9
Buoying Up When the buoyant force on an object is greater
than the object’s weight, the object is buoyed up (pushed up) in water.
FORCES in FLUIDS
Chapter 7
Mr. Swope
between fluid pressure
and buoyant force.
Predict whether an object
will float or sink in a fluid.
Analyze the role of
density in an object’s
ability to float.
Will an object sink or float? That depends on the whether the buoyant force is
less than or equal to the object’s weight.
Sinking
A rock that weighs 75 N, but displaces 15 N of water will sink.
Floating
A duck may weigh 9 N and displaced 9 N of water, so the duck will float.
Buoying up
When the buoyant force on an object is greater than the objects weight, the
object is buoyed up or pushed up in the water.
Sinking, Sinking, and Density
more dense than air will sink and air.
Objects less dense than air will float in air.
Objects
Finding Density
Explain three methods
that the overall density of
an object can be changed.
Changing Overall Density
•
Changing Shape The secret of how a ship floats is in the shape of the
ship. Ships made of steel float because their overall density is less than
the density of water.
steel, which is almost 8 times
Explain the relationship
between fluid pressure
and buoyant force.
Predict whether an object
will float or sink in a fluid.
Analyze the role of
density in an object’s
ability to float.
Explain how the overall
density of an object can
be changed.
This demonstrates how a ship made out of
denser than water, is able to float in water.
•
•
•
Changing Mass
A submarine is a special kind of ship that
can travel both on the surface of the water and underwater.
Submarines have ballast tanks that can be opened to allow sea water to
flow in.
water
As
is added, the submarine’s mass increases, but its volume
stays the same.
Compressed air is used to blow the water out of the tanks so the submarine can
rise.
Changing volume
•
Lesson three essential
question
What is the relationship
between pressure and
fluid speed?
What is the role of lift,
thrust, and wing size inPage
10
Changing Volume Like a submarine, some fish adjust their overall
density to stay at a certain depth in the water.
Most bony fishes have an organ called a swim bladder which helps them change
volume.
End of lesson two
FORCES in FLUIDS
Chapter 7
Mr. Swope
flight?
What is a description of
drag, and how does it
affect lift?
What is Pascal's principle?
Lesson Three
Fluids and Motion
Fluid Speed and Pressure
Bernoulli’s principle states that as the speed of a moving fluid increases, the
fluid’s pressure decreases.
Lesson Three Terms
Bernoulli’s principle
Lift
Thrust
Drag
Pascal’s principle
Describe to a classmate the relationship between pressure and fluid speed.
Factors That Affect Flight
Describe to a classmate
drag, and explain how it
affects lift.
Thrust and Lift
•
Thrust is the forward force produced by a
plane’s engine. Lift is the upward force on the wing as it moves through
the air.
•
Wing Size, Speed, and Lift
which also helps it move faster.
Smaller wings keep a plane’s weight low,
Bernoulli and Birds A small bird must flap its small wings at a fast pace
to stay in the air, but a large bird flaps less.
Analyze with a classmate the roles of lift, thrust, and wing size in flight.
Lesson three evaluation
Describe the relationship
between pressure and
fluid speed.
Analyze the roles of lift,
thrust, and wing size in
flight.
Explain Pascal’s principle.
Describe drag, and explain
how it affects lift.
Bernoulli and Baseball The next slide shows how a baseball pitcher can
take advantage of Bernoulli’s principle to throw a curveball.
Drag and Motion in Fluids
•
Drag is the force that opposes or restricts motion in a fluid. It is a
•
•
force that is parallel to the velocity of the flow.
Drag is usually caused by an irregular flow of air, known as turbulence.
Turbulence and Lift
Lift is often reduced when
turbulence causes drag.
Pascal’s Principle
•
Pascal’s
What Is
Principle? Pascal’s principle states that a
change in pressure at any point in an enclosed fluid will be transmitted
equally to all parts of that fluid.
Pascal’s
Pascal’s Principle and Motion Hydraulic devices use
principle to
move or lift objects. Liquids are used in hydraulic devices because liquids cannot
be easily compressed into a smaller space.
Because of Pascal’s principle, the touch of a foot can stop tons of moving metal.
End Of Lesson Three
End of Chapter 7
Page
11
FORCES in FLUIDS
Chapter 7
Mr. Swope
Page
12
FORCES in FLUIDS
Chapter 7
Mr. Swope
Fluid
Pressure
Page
13
FORCES in FLUIDS
Chapter 7
Mr. Swope
Calculating
Pressure
Paschal
Page
14
FORCES in FLUIDS
Chapter 7
Mr. Swope
Atmospheric pressure
Buoyant force
Archimedes Principle
Bernoulli’s Principle
Page
15
FORCES in FLUIDS
Chapter 7
Mr. Swope
Lift
Thrust
Drag
Page
16
FORCES in FLUIDS
Chapter 7
Mr. Swope
Pascal’s principle
Page
17