The document summarizes key concepts about fluids and their properties. It explains that fluids exert pressure evenly, and pressure increases with depth. It also discusses how atmospheric pressure varies with altitude. Objects float based on buoyant force balancing their weight. Denser objects sink while less dense objects float. Fluids flow from high to low pressure. The document also examines how fluid speed relates to pressure through Bernoulli's principle and how wing design and size influence flight.

1. Book M – Chapter 3

2. Warmup
One afternoon, you go outside to find your younger
sister standing by her bike with a nail in her hand. The
bike has a flat tire. She wants to know why the air
came out of the tire when she pulled the nail out.
Write a few sentences to explain why air rushes out of
a hole in a tire.

3. Taking Flight
p.65

4. Section 1: Fluids and Pressure
By the end of this section, you should be able to:
 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.

5. Fluids Exert Pressure
 A fluid is any material that can flow and that takes
the shape of its container. Fluids include liquids and
gases.
 All fluids exert pressure, which is the amount of force
exerted per unit area of a surface.

6. Fluids Exert Pressure
 In a tire the force of the air particles hitting the inner
surface of the tire creates pressure, which keeps the
tire inflated.

8. Calculating Pressure


10. Fluids Exert Pressure
 When you blow a soap bubble, why does it get
rounder instead of just longer?
 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.

11. Atmospheric Pressure
 The atmosphere 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.
 Atmospheric pressure is exerted on everything on
Earth, including you.

12. Atmospheric Pressure
 The air inside a balloon exerts pressure that keeps
the balloon inflated against atmospheric pressure.

13. 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.
 As you travel through the atmosphere,
atmospheric pressure changes. The
further down through the atmosphere
you go, the greater the pressure is.

14. Atmospheric Pressure
 If you travel to higher or lower points in the
atmosphere, the fluids in your body have to adjust to
maintain equal pressure.
 You may have experienced this adjustment is your
ears have “popped” when you were in a plane taking
off or in a car traveling down a steep mountain road.

15. Water Pressure
 Water is a fluid. So, it exerts pressure
like the atmosphere does.
 Like atmospheric pressure, water
pressure depends on depth.

16. Water Pressure
 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.

17. 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.
 Exhaling causes fluids to flow from high to low
pressure.

19. Pressure Differences and Fluid Flow
 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.

20. How Do Droppers Work?
Experiment with the dropper and water and then write
a paragraph talking about how the dropper works.
Make sure to talk about why water goes up into the
dropper and why the water can be forced out.

21. Section 1 Review
p.71 #2-8, 10

22. Warmup
Identify which of the following objects will float in
water: a rock, an orange, a screw, a quarter, a candle,
a plastic-foam “peanut,” and a chalkboard eraser.
Write a hypothesis about why an aircraft carrier, which
weighs thousands of tons, does not sink.

23. Section 2: Buoyant Force
By the end of this section, you should be able to:
 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.

24. Buoyant Force and Fluid Pressure
 Buoyant force is the upward force that keeps an
object immersed in or floating on a liquid.
 Archimedes’ 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.

25. 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 buoyant force on the object.

26. Weight vs. Buoyant Force
 An object in a fluid will sink if its weight is greater
than the buoyant force.
 An object will float only when the buoyant force on
the object is equal to the object’s weight.
 When the buoyant force on an object is greater than
the object’s weight, the object is buoyed up (pushed
up) in water.

27. Weight vs. Buoyant Force
 Will an object sink or float? That depends on the
whether the buoyant force is less than or equal to
the object’s weight.

29. Floating, Sinking, and Density
 Ice floats on water because it is less dense than
water. Ice, like most substances, is more dense than
air. So, ice does not float in air.
 One substance that is less dense than air is helium
gas. A given volume of helium displaces an equal
volume of air that is much heavier than itself. So,
helium floats in air.

31. Ship Shape Quick Lab
p.76

32. Changing Overall Density
 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.
 A ship made out of steel, which is almost 8 times
denser than water, is able to float in water.

34. Changing Overall Density
 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 water is added, the submarine’s mass increases,
but its volume stays the same.

36. Changing Overall Density
 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.

37. Section 2 Review
p.77 #2-7

38. Warmup
You have been asked to design two kites. One kite will
be flown in areas where there is almost always a good
breeze. The other kite will be flown in areas with very
little wind.
What differences in design and materials are there
between your two kites?

39. Section 3: Fluids in Motion
By the end of this section, you should be able to:
 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.

40. Magic Water – Straw Demo

41. What’s Going On?
 Hold 2 sheets of paper so that the edges are in front
of your face about 2 inches apart. The flat faces of
the paper should be parallel to each other.
 Blow as hard as you can between the two sheets of
paper.
 Write down your observations and what you think is
happening.

42. Science in the Sink

43. Fluid, Speed, and Pressure
 Bernoulli’s principle states that as the speed of a
moving fluid increases, the fluid’s pressure
decreases.
 A table-tennis ball is attached to a string and swung
into a stream of water, where it is held. Because the
water is moving faster than air, the ball is pushed by
the higher pressure of the air into an area of reduced
pressure - the water stream.

44. Ping Pong Balls Defying Gravity

45. 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.
 Smaller wings keep a plane’s weight low, which also
helps it move faster.
 A small bird must flap its small wings at a fast pace
to stay in the air, but a large bird flaps less.

48. 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.
 Lift is often reduced when turbulence causes drag.

49. Pascal’s 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.
 Hydraulic devices use Pascal’s principle to move or
lift objects. Liquids are used in hydraulic devices
because liquids cannot be easily compressed into a
smaller space.

50. Pascal’s Principle
 Because of Pascal’s principle, the touch of a foot can
stop tons of moving metal.

51. Section 3 Review
p.83 #3-9